Introduction - PETROL INJECTION SYSTEM

1.6 16v · Euro 3

MARELLI IAW 4EF EOBD FUEL INJECTION

CONSTRUCTION FEATURES

The Marelli IAW 59F system belongs to the category of systems integrated with:

• inductive discharge digital electronic ignition
• distributorless
• sequential, phased electronic injection (1-3-4-2)

1, Safety and ventilation valve

2, Fuel tank

3, Electric fuel pump

4, Idle speed actuator

5, Radiator fan high and low speed relay feeds

6, Battery

7, Ignition switch

8, Injection system relay

9, CODE control unit

10, Inertia switch

11, Vehicle speed sensor

12, Diagnostic socket

13, Rev counter

14, Injection system failure warning light

15, Fuses protecting injection/ignition system

16, General protective fuse box

17, Butterfly valve position sensor

18, Fuel supply manifold

19, Injectors

20, Air filter

21, Spark plugs

22, Ignition coils

23, Engine coolant temperature gauge

24, Air temperature and pressure sensor

25, Rpm and T.D.C. sensor

26, Detonation sensor

27, Coolant temperature sensor

28, Fuel vapour solenoid valve

29, Active charcoal filter

30, Climate control compressor

31, Lambda sensor (precatalyzer)

32, Catalytic silencer

33, Injection/ignition control unit

34, Multi-purpose valve

35, Engine coolant overheating warning light

36, Climate control compressor relay

37, Climate control system relay

38, Lambda sensor (post catalyzer)

39, Injection timing sensor

General characteristics

Operation of the injection/ignition system

During idling, the control unit checks:

• the ignition instant
• the air flow with the benefit of maintaining correct operation of the engine when the environmental parameters and applied loads vary.

The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

The system's functions are basically as follows:

• system self-adaptation;
• self-test
• recognition of FIAT CODE
• control of cold starting
• control of combustion - Lambda sensor
• control of detonation
• control of mixture enrichment during acceleration
• fuel cut-off during overrunning
• fuel vapour recovery
• limitation of the maximum rpm
• control of fuel-electric fuel pump supply
• connection to the climate control system
• recognition of cylinder position
• adjustment of injection times
• adjustment of ignition advance values
• control and management of the idle speed
• control of electric cooling fan.
• diagnosis of 'Fuel System'
• diagnosis of catalyzer
• diagnosis of Lambda sensors
• diagnosis of 'Misfire'

Fuel injection system

The essential conditions that must always be met in the preparation of the air-fuel mixture for the correct operation of controlled-ignition engines are mainly:

• the 'metering' (air/fuel ratio) must constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the necessary rapidity of combustion, avoiding unnecessary fuel consumption
• the 'homogeneity' of the mixture, consisting of petrol vapours, diffused as finely and evenly as possible in the air.

The injection/ignition system uses an indirect measuring system known as the 'SPEED DENSITY LAMBDA type. In other words the angular rotation speed, density of the intake air and control of the mixture strength.

In practice the system uses data on the ENGINE SPEED (rpm) and AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.

The quantity of air drawn in by each cylinder, for each engine cycle depends not only on the density of the intake air, but also on the unit displacement and the volumetric efficiency.

The density of the air refers to that of the air drawn in by the engine and calculated according to the absolute pressure and the temperature, both detected in the inlet manifold by specific sensors.

Volumetric efficiency refers to the parameter relating to the coefficient for filling the cylinders measured on the basis of experimental tests carried out on the engine throughout the entire operating range and then stored in the electronic control unit memory.

Having established the quantity of intake air, the system has to provide the quantity of fuel according to the desired mixture strength.

The end of injection impulse or supply timing is contained in a map stored in the control unit memory and varies according to the engine speed and the pressure in the inlet manifold. In practice, it involves processing which the electronic control unit carries out to command the sequential, phased opening of the four injectors, one per cylinder, for the length of time strictly necessary to form the air/petrol mixture which is closest to the stoichiometric ratio.

The fuel is injected directly into the manifold near the inlet valve at a pressure of around 3 bar.

Whilst the speed (rpm) and the density of the air (pressure and temperature) are used to measure the quantity of intake air, which when established allows the quantity of fuel to be metered according to the desired mixture strength, the other sensors in the system (coolant temperature, butterfly valve position, battery voltage, etc.) allow the electronic control unit to correct the basic strategy for all engine operating conditions.

It is vital for the air/fuel ratio to be around the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for the reduction of pollutant emissions.

Ignition system

The ignition is the inductive discharge type, i.e. without a high tension distributor, with power modules located in the electronic injection/ignition control unit.

The system has two high tension twin outlet coils joined in a single container and connected directly to the spark plugs.

The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage) and to the pins for the electronic control unit for connection to earth.

After the starting stage, the electronic unit manages the basic advance taken from a special map according to the:

• engine rpm
• absolute pressure value (mmHg) measured in the inlet manifold.

This advance value is corrected according to the temperature of the engine coolant and the intake air.

The spark plugs for cylinder 1-4 and 2-3 are connected directly (two at a time) by means of high tension leads to the terminals of the coil secondary winding and their connection is in series because the cylinder head joins them. This solution is also known as the 'lost spark' becuse the energy accumulated by the coil is almost exclusively discharged at the electrodes for the spark plug of the cylinder under compression allowing the ignition of the mixture. The other spark is obviously not used, as no mixture is found in the cylinder to ignite, only exhaust gas.

OPERATION

Diagram of input/output info to/from control unit

1, Electronic control unit

2, Speedometer sensor

3, CODE control unit

4, Engine idle speed actuator

5, Fuel injectors

6, Fuel vapour solenoid valve

7, Diagnostic socket

8, Spark plugs

9, Ignition coils

10, Engine coolant overheating warning light

11, Injection failure warning light

12, Climate control system

13, Engine coolant temperature sensor

14, Intake air temperature and pressure sensor

15, Butterfly valve position sensor

16, Detonation sensor

17, Rpm and TDC sensor

18, Injection timing sensor

19, Ignition switch

20, Lambda sensor (pre catalyzer)

21, Lambda sensor (post catalyzer)

22, Electric fuel pump

23, Radiator fan high and low speed relay feeds

24, Rev counter / speedometer

Operating strategy

System self-adaption

The control unit has a self-adaption function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.

These changes are stored in the form of modifications to the basic mapping, and their purpose is to adapt the operation of the system to the gradual alterations in the engine and components compared with their characteristics when new.

This self-adaptation function also makes it possible to even out inevitable differences (due to production tolerances) in any replaced components.

From the exhaust gas analysis, the control unit changes the basic mapping in relation to the original characteristics of the new engine

The self-adaptation parameters are not cancelled if the battery is disconnected.

Self-testing

The control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram. This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

• with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The control unit's self-test checks the signals coming from the sensors, comparing them with the permitted limits:

Signalling of faults during engine starting:

• the failure of the warning light to go out once the engine has been started up means that there is an error memorized in the control unit.

Fault indication during operation

• the warning light flashing indicates possible damage to the catalyzer due to misfire.
• the warning light on constantly indicates the presence of engine management errors or EOBD errors.

RECOVERY

From time to time, the control unit defines the type of recovery according to the components which are faulty.

The recovery parameters are managed by those components which are not faulty.

Recognition of the code

When the control unit receives the ignition 'ON signal, it communicates with the CODE control unit to obtain starting enablement.

Communication takes place via the dedicated bidirectional serial diagnostic line which connects the two control units.

Control of combustion - lambda sensors

In EOBD systems the Lambda sensors, which are all the same type, are located upstream of the catalyzer and downstream of the catalyzer. The upstream sensors carry out the check on the mixture strength known as the 1st loop (upstream sensor closed loop). The sensor downstream of the catalyzer is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters. With this in mind, the adjustment of the second loop is designed to recover both production differences and those in the response of the upstream sensors which may occur as a result of ageing and pollution. This control is known as the 2nd loop (downstream sensor closed loop).

Operation when cold

Under these circumstances there is a natural weakening of the mixture because of the poor turbulence of the fuel particles at low temperatures, reduced evaporation and condensation on the inner walls of the inlet manifold, all of which is exacerbated by the increased viscosity of the lubricant oil which, as is well known, increases the rolling torque of the engine mechanical components at low temperatures.

The electronic control unit recognizes this condition on the basis of the coolant temperature signal, increasing the basic injection time.

Whilst the engine is warming up, the electronic control unit also operates the stepping motor which determines the quantity of air needed to ensure that the engine does not cut out.

Operation in full load conditions

Operation in full load conditions is detected, by the control unit, through the values supplied by the butterfly position and absolute pressure sensors.

In full load conditions, the basic injection time must be increased to obtain the maximum power supplied by the engine.

Operation in deceleration conditions

During this stage the engine has two strategies:

• A negative, transitory strategy to keep the quantity of fuel supplied to the engine at the stoichiometric value (less pollution). This stage is recognized by the control unit when the butterfly potentiometer signal goes from a high voltage reading to a lower one.
• A soft accompaniment strategy at the lower speed (dash-pot) to lessen the variation in the torque supplied (reduced engine braking).

Barometric correction

The atmospheric pressure varies according to the altitude creating a variation in the volumetric efficiency which requires the correction of the basic mixture strength (injection time).

The correction of the injection time depends on the variation in altitude and is automatically updated by the electronic control unit each time the engine is switched off and in certain butterfly position and rpm conditions (typically at low speeds and with the butterfly wide open) (dynamic adjustment of barometric correction).

Operation during cut-off

The cut-off strategy is implemented when the control unit recognizes the butterfly valve in the idle position (butterfly potentiometer signal) and the engine speed exceeds 1350 rpm. The control unit only enables the cut-off when the engine temperature exceeds 0° C.

The recognition of the butterfly valve in a non closed position or the engine speed below 1270 rpm enables the supply to the engine.

For very high speeds the cut-off is implemented even when the butterfly is not completely closed, but when the pressure in the inlet manifold is particularly low (partial cut-off).

Operation in acceleration conditions

During this stage, the control unit increases the quantity of fuel requested by the engine as appropriate (to achieve maximum torque) according to the signals coming from the following components:

• butterfly potentiometer;
• rpm and T.D.C. sensor.

The 'basic' injection time is multiplied by a coefficient which depends on the temperature of the engine coolant, the opening speed of the accelerator butterfly and the increase in pressure in the inlet manifold.

If the sharp variation in the injection time is calculated when the injector is already closed, the control unit reopens the injector (extra pulse) in order to compensate the mixture strength extremely quickly; the subsequent injections are already increased on the basis of the coefficients mentioned previously.

Protection against excess rpm

When the engine rotation speed exceeds 6700 rpm for more than 10 seconds or reaches the 'limit' of 6900 rpm, set by the manufacturer, the engine finds itself operating in 'critcal' conditions.

When the electronic control unit recognizes that the above speed has been exceeded, it prevents the operation of the injectors.

When the rotation speed returns to a non critical value, the operation is resumed.

Fuel pump control

The electric fuel pump is controlled by the engine control unit by means of a relay.

The pump cuts out:

• if the engine speed goes below about 50 rpm
• after a certain period (about 5 seconds) with the ignition switch in the ON position without the engine being started up (timed go ahead)
• if the inertia switch has operated.

Injector operation

The operation of the injectors is the sequential, phased type. However, during starting the injectors are operated once in parallel (full-group).

The timing of the injector operation varies according to the engine speed and pressure of the inlet air in order to improve the filling of the cylinders with advantages in terms of consumption, driveability and pollution.

Knock control

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor. The strategy continuously compares the signal coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

If the system recognizes the presence of detonation, the strategy reduces the ignition advance until the phenomenon disappears. Later, the advance is gradually restored to the basic value or until the phenomenon occurs again. In particular, advance increases are implemented gradually, whilst reductions are implemented immediately.

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The strategy also features a self-adaptation function which temporarily memorizes the reductions in the advance that may be continuously repeated, in order to adjust the advance to the different engine operating conditions (for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to the threshold value memorized when the conditions which have caused the reduction no longer exist.

Management of radiator fan

The control unit directly controls the operation of the radiator fan according to the temperature of the engine coolant and the engagement of the climate control system.

The fan is switched on when the temperature exceeds 98°C (1st speed) and 101°C (2nd speed). The switching off takes place with a hysteresis of 2°C below the engagement threshold.

The high and low speed functions are managed by the intervention of special relays in the climate control system control unit and are operated by the control unit.

Management of the engine idle

The general aim of this strategy is to keep the engine idling at around the value memorized (engine warm: 850 rpm); the position of the actuator depends on the following engine conditions:

• During starting. When the key is inserted, the position of the actuator depends on the temperature of the engine coolant and the voltage of the battery (open-loop position).
• Warming up stage. The engine speed is corrected, particularly on the basis of the engine coolant temperature.
• With the engine at operating temperature, the management of the idle depends on the signal coming from the rpm sensor; when external loads are applied, the control unit manages the sustained idle.
• Deceleration stage. In deceleration conditions outside of idling, the control unit controls the position of the engine idle speed actuator by means of a special flow rate curve (dash-pot curve), in other words it slows down the return of the shutter towards its seating, improving the braking effect of the engine.

Recognition of cylinder position

The engine timing signal, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognize the succession of cylinders to implement phased injection.

This signal is generated by a Hall-effect sensor, positioned on the cylinder head near the phonic wheel on the inlet camshaft.

Management of fuel vapour recirculation

This strategy controls the position of the vapour cut out solenoid valve in the following way:

• during starting the solenoid remains closed, preventing the fuel vapours from enriching the mixture too much; this condition persists until the temperature of the coolant temperature reaches 65° C;
• with the engine at operating temperature, the electronic control unit sends the solenoid valve a square wave signal (duty-cycle operation) and the opening is modulated.

In this way the control unit controls the quantity of fuel vapours sent to the inlet, preventing considerable variations in the mixture strength.

In the operating conditions listed below:

• butterfly valve in closed position
• engine speed below 1500 rpm
• inlet manifold pressure below the limit calculated by the control unit depending on the number of revs; the control of the solenoid is inhibited and the latter remains closed; this improves engine operation.

Management of the climate control system

The injection/ignition control unit is connected to the climate control system in that:

• it receives the request to switch on the compressor and make the related interventions (additional air);
• it gives the go ahead to switch on the compressor, when the conditions covered by the strategies have arisen;
• it receives information on the state of the four stage pressure switch and makes the appropriate interventions (radiator fan operation).

If the engine is idling, the control unit increases the flow rate of the air passing from the idle actuator before the compressor is switched on and, viceversa, it returns the actuator to the normal position after the compressor is switched off.

The control unit automatically controls the disengagement of the compressor:

• at engine coolant temperatures above a certain level
• at engine speeds below 750 rpm.

The control unit temporarily controls the disengagement of the compressor (for a few seconds):

• during high power requests from the engine (strong acceleration)
• during engine pickup.

Recovery

AIR TEMPERATURE SENSOR

If the error is present during starting:

• it assumes a value of 50 °C
• self-adjustment of the mixture strength is inhibited.

If the error is present in other conditions:

• the last valid value is memorized and updated according to the coolant temperature.

DETONATION SENSOR

If the sensor is faulty, the engine control unit implements more conservative ignition advance 'maps' to safeguard the engine.

LAMBDA PROBES

In the case of a failure, the information transmitted is ignored and the system operates in open-loop.

PRESSURE SENSOR

If the failure is present during starting, it uses a value of 1024 mbar. During operation the value used is calculated on the basis of parameters supplied by the butterfly valve position sensor and the rpm sensor. Self-adjustment of the mixture strength is inhibited.

THROTTLE POSITION SENSOR

In the case of a fault, a value calculated from the absolute pressure sensor readings is set, and if this sensor is broken, a fixed value equal to a butterfly opening of 50 degrees is set. The mixture strength and idle self-adjustment dash-pot strategies are suspended.

VEHICLE SPEED SENSOR

The last vehicle speed value memorized when there was no error is assumed.

COOLANT TEMPERATURE SENSOR

In the case of a failure the ECU inhibits the self-adjustment of the mixture strength and idle. It sets the last temperature value measured; If this does not correspond, the ECU increases it gradually according to the time since the engine was started up until it reaches 80 °C. The radiator cooling fan is operated.

ENGINE IDLE SPEED ACTUATOR

In the event of a fault, the operation of the actuator is disabled and self-adjustment of the idle mixture strength is stopped.

Iaw 4ef injection/ignition control unit

The engine unit is fitted in the engine compartment and is capable of withstanding high temperatures.

It is a digital type with a microprocessor, featuring a high calculation capacity, precision, reliability, versatility and low energy consumption and is maintenance-free.

The task of the electronic control unit is to process the signals coming from the various sensors through the application of software algorithms and control the operation of the actuators (in particular the injectors, ignition coils and idle actuator) in order to ensure optimum engine operation.

The adoption of the CODE does not allow control units to be exchanged between cars.

Pins

1, Earth for pre catalyzer Lambda sensor heater

2, Earth for post catalyzer Lambda sensor heater

3, Not connected

4, Rev counter signal

5, Automatic transmission control unit (coolant temperature)

6, Not connected

7, Not connected

8, Not connected

9, Pre catalyzer Lambda sensor (negative)

10, Not connected

11, Not connected

12, Post catalyzer Lambda sensor (negative)

13, CODE control unit

14, Radiator fan high speed control

15, Injection system relay go ahead

16, Butterfly position signal (automatic transmission only)

17, Engine coolant overheating warning light

18, Not connected

19, Not connected

20, Pre catalyzer Lambda sensor (positive)

21, Radiator fan high speed request signal

22, Not connected

23, Fuel level signal

24, Post catalyzer Lambda sensor (positive)

25, Diagnostic socket (line K)

26, Injection system failure warning light (EOBD)

27, Earth

28, Earth

29, Supply (+30) with fuse

30, Not connected

31, Not connected

32, Not connected

33, Not connected

34, Not connected

35, Radiator fan low speed request signal

36, Torque reduction signal (automatic transmission only)

37, Not connected

38, Not connected

39, Not connected

40, Radiator fan low speed control

41, Air conditioning compressor relay

42, Not connected

43, Not connected

44, Lambda sensors cable screening

45, Not connected

46, Not connected

47, Supply (+15)

48, Air conditioning engagement request

49, Gear lever position signal (automatic transmission only)

50, Vehicle speed signal

51, Not connected

52, Fuel vapour solenoid valve

53, Rpm sensor (positive)

54, Sensor earth

55, Intake air temperature signal

56, Knock sensor (positive)

57, Engine idle speed actuator

58, Engine idle speed actuator

59, Ignition coils (cylinders 1-4)

60, Butterfly position sensor supply

61, Not connected

62, Engine coolant temperature sensor

63, Detonation sensor cable screening

64, Engine idle speed actuator

65, Engine idle speed actuator

66, Ignition coils (cylinders 2-3)

67, Rpm sensor (negative)

68, Sensor supply

69, Timing sensor

70, Detonation sensor (negative)

71, Injector for cylinder n°1

72, Injector for cylinder n°4

73, Not connected

73, Fuel consumption signal

75, Intake air pressure signal

76, Butterfly position signal

77, Rpm sensor cables screening

78, Injector for cylinder n°3

79, Injector for cylinder n°2

80, Not connected

Fuel injectors

Specifications

The twin jet injectors are specifically designed for engines with 4 valves per cylinder, making it possible to direct the jets towards the two inlet valves.

The injectors are fixed by the fuel manifold, which presses them into their seats in the inlet ducts. They are also secured to the fuel manifold by means of 'safety clips'.

Two Viton sealing rings ensure a seal on the intake duct and manifold

Operation

The jets of fuel, at a differential pressure of about 3.5 bar, come out of the injector and are instantly atomized forming two cones.

The control logic for the injectors is the 'sequential phased type', in other words the four injectors are operated according to the inlet sequence of the engine's cylinders.

Fuel manifold

Specifications

The upper part is made from plastic whilst the lower part is produced by aluminium die-casting and incorporates the seats for the injectors.

The fuel manifold is fixed to the inner part of the inlet manifold and its function is to send the fuel to the injectors.

Engine coolant temperature sensor

Specifications

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

One NTC thermistor sends the signal to the injection control unit whilst the other one sends the signal to the temperature gauge and warning light.

The sensor is based on semiconductor technology; so if the sensor temperature increases as the water temperature increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

1, Engine earth

2, Temperature gauge on instrument panel

3, Electrical connection

4, Motor metal casing

5, Engine earth

6, NTC for thermometer

7, NTC fuel injection

Detonation sensor

Specifications

The piezoelectric detonation sensor is mounted on the engine block, and it detects the intensity of vibrations caused by knocking in the combustion chambers.

This phenomenon produces a mechanical repercussion on a piezoelectric crystal which sends a signal to the control unit.

On the basis of this input signal, the control unit reduces the ignition advance until the phenomenon disappears. The advance is then gradually restored to the basic value.

Operation

The molecules of a quartz crystal are electrically polarised.

In rest conditions (A) the molecules do not have a particular direction.

When the crystal is subjected to pressure or an impact (B); their direction is all the more marked the greater the pressure to which the crystal is subjected. This direction produces a voltage at the ends of the crystal.

A, Rest position

B, Position under pressure

Electrical characteristics

Resistance between pin 1 and pin 2: 560 ± 28 ohm

Rpm sensor

Specifications

It is mounted on the engine block and 'faces' the phonic wheel located on the crankshaft.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the flywheel (60-2 teeth).

The control unit uses the rpm sensor signal for determining the rotation speed and for determining the angular position of the crankshaft.

Components

The sensor consists of a tubular casing (1) which contains a permanent magnet (3) and an electrical winding (2).

Operation

As the flywheel teeth go past, the magnetic flow created by the magnet undergoes fluctuations due to the change in gap.

These fluctuations induce an electromotive force in the winding (2), at the ends of which there is a voltage which alternates between positive (tooth opposite sensor) and negative (gap opposite sensor).

The peak value of the output voltage from the sensor, provided other factors remain the same, depends on the distance between the sensor and tooth (gap).

The phonic wheel comprises sixty teeth, two of which have been removed to create a reference: the pitch of the wheel thus corresonds to an angle of 6° (360° divided by 60 teeth). The synchronization point is recognized at the end of the first tooth after the space created by the two missing teeth: when this passes under the sensor, the pair of pistons 1-4 of the engine are at 114° before TDC.

The specified gap for obtaining correct signals, between the end of the sensor and the phonic wheel, must be between 0.5 and 1.5 mm.

Electrical characteristics

Resistance: 1134-1386 ohm at 20 °C

Throttle body

Specifications

This has the task of metering the amount of air supplied to the engine according to the request from the driver via the accelerator.

The butterfly is opened by means of non linear linkage which, depending on the accelerator pedal travel, produces small butterfly opening angles in the first section of the pedal travel and, conversely, greater angles with the pedal very depressed.

With the pedal completely released, the additional air required is supplied by the idle speed actuator.

Under these circumstances, the throttle opening lever comes up against an anti-tamper screw which prevents the throttle from getting stuck in the closed position.

To avoid condensation and the formation of ice which could occur in certain conditions when the outside temperature is very low and/or it is very damp, the butterfly casing is heated with a small amount of coolant coming from the engine thermostat made to circulate in a chamber inside the actual casing.

The throttle position sensor and the engine idle speed actuator are also fitted on the throttle body.

The anti-tamper screw is regulated during the fluxing operation in the factory and should never be tampered with.

Throttle position sensor

Specifications

This sensor consists of a potentiometer where the moving part is controlled by the butterfly valve shaft.

The potentiometer is of linear type (single ramp); its main characteristics are:

• total mechanical travel from 0° to 105°
• useful electrical angle from 88° to 92°
• temperature operating range from -30°C to +125°C.

Operation

The control unit provides the potentiometer with a 5 Volt supply. The parameter measured is the butterfly position from minimum to full opening for management of injection.

On the basis of the output voltage, the control unit recognizes the butterfly valve opening condition and suitably corrects the mixture strength.

With the butterfly closed, an electrical voltage signal is sent to the control unit which recognizes the idle and cut-off conditions (distinguishing between them on the basis of the engine speed).

The sensor does not require any sort of adjustment to its angular position because it is the control unit which, by means of suitable self-adjustment algorithms, recognizes that the butterfly is fully closed or fully open.

The potentiometer is the single ramp type and does not need to be adjusted because the control unit programme learns the butterfly idle position (0 - 950 mV). The fastening of the potentiometer to the butterfly casing is the SNAP-IN type.

Engine idle speed actuator (step motor)

Specifications

The actuator is fitted on the butterfly casing and consists of:

• an electrical stepping motor with two windings in the stator and a rotor composed of two permanent magnet poles
• a screw-female screw type reduction gear which transforms the rotary motion into linear motion of the shutter.

1, Bearing

2, Nutscrew

3, Coils

4, Magnet

5, Screw

6, Anti-rotation splining

7, Shutter

The electrical stepper motor features a high degree of precision and rapid resolution (about 200 steps per second). The impulses sent by the electronic control unit to the engine are transformed from a rotary motion into a linear motion (about 0.04 mm/step) by means of a screw-female screw type mechanism, operating the shutter whose movements alter the section of the by-pass duct.

The constant value of the minimum air flow rate (Q0) is due to the flow under the butterfly valve which is regulated in production and guaranteed by an anti-tamper plug.

The maximum flow rate (Q2) is guaranteed by the shutter in the fully retracted position (about 200 steps corresponding to 8.8 mm). The law shown in the graph below applies between these two air flow rate values.

Q, Air flow rate regulated by the actuator (variable)

Q0, Air flow rate escaping from the butterfly (constant)

Operation

In order to idle, i.e. with the butterfly (4) completely closed, the engine requires a certain amount of air (Q0) and fuel to overcome the internal friction and sustain its rotation speed.

To the quantity of air (Q0) arriving from the filter which, during idling, flows through the butterfly valve (4) in a closed position, it is necessary to add, when the engine is warming up or when electrical consumers are switched on or outside loads applied (air conditioning etc.), a further quantity of air (Q) to allow the engine to keep the rotation speed constant.

To achieve this result the system uses a stepping motor operated by a circuit inside the injection/ignition electronic control unit which, when operating, moves a rod fitted with a plunger which alters the section of the by-pass duct and, consequently, the quantity of air (Q0 + Q) drawn in by the engine.

To adjust this type of action, the electronic unit uses the engine angular speed and coolant temperature parameters, coming from the respective sensors.

The fastening for the stepping motor on the butterfly casing is the SNAP-IN type.

Intake air temperature and pressure sensor

Specifications

The sensor is fitted on the inlet manifold and is a built-in component. It records pressure and temperature inside the intake manifold. Both pieces of information are used by the injection control unit to define the quantity of air drawn in by the engine. This information is then used to calculate the injection time and the point of ignition.

Operation

Air temperature sensor

The air temperature sensor consists of an NTC thermistor (Negative Temperature Coefficient). The resistance of the sensor decreases as the temperature increases. The control unit input circuit divides the 5 Volt reference voltage between the sensor resistance and a fixed reference value, obtaining a voltage which is proportional to the resistance and therefore to the temperature.

THERMISTOR SPECIFICATIONS

(*) control temperature

Pressure sensor

The sensitive element of the pressure sensor consists of a Wheatstone bridge on a ceramic diaphragm. On one side of the diaphgram is the absolute reference vacuum, whilst the vacuum from the inlet manifold acts on the other side. The (piezoresistive) signal from the distortion suffered by the diaphgram, before being sent to the engine control unit, is amplified by an electronic circuit in the support which also houses the ceramic diaphragm. When the engine is off, the diaphragm bends in accordance with the atmospheric pressure; the correct altitude information is thus obtained.

When the engine is running, the effect of the vacuum produces a mechanical action on the sensor diaphgram, which bends, altering the resistance value.

Since the supply is kept rigourously constant (5V) by the control unit, altering the resistance, alters the voltage output value.

Static ignition coil with four high tension outputs

Specifications

The ignition coils are fixed by a bracket to the camshaft covers.

They are the closed magnetic circuit type with a core made from silicon steel with a thin gap containing both windings.

The windings are covered by a moulded plastic container and are insulated by embedding in an epoxy resin and quartz compound which gives them exceptional dielectric, mechanical and thermal properties enabling them to withstand high temperatures. The proximity of the primary winding to the magnetic core reduces the magnetic flow losses optimizing the coupling with the secondary winding.

1, High tension output for cylinder 1 spark plug

2, High tension output for cylinder 2 spark plug

3, High tension output for cylinder 3 spark plug

4, High tension output for cylinder 4 spark plug

5, Low tension socket for control unit connection

Wiring diagram

1, High tension output for cylinder 1 spark plug

2, High tension output for cylinder 2 spark plug

3, HIgh tension output for cylinder 3 spark plug

4, High tension output for cylinder 4 spark plug

5, Low tension connector

5a, Control for cylinders 2 and 3

5b, Battery positive

5c, Control for cylinders 1 and 4

6, Gap

Timing sensor

Specifications

This system uses a sequential phased injection system, i.e. the fuel injection takes place in sequence for each cylinder at the intake stage.

To do this, in addition to the rpm and TDC signal, the electronic unit also uses another signal to determine the injection point. The signal sent to the control unit is produced by a Hall-effect sensor (2) mounted level with the inlet side camshaft drive pulley.

1, Fixing bolts

2, Hall-effect sensor

3, Inlet side camshaft pulley

Principle of operation

A semiconducting layer, through which current passes, immersed in a perpendicular magnetic field (force lines perpendicular to the current direction), generates at its ends a difference in potential known as Hall voltage.

If the intensity of the current remains constant, the voltage generated only depends on the intensity of the magnetic field; the intensity of the field simply has to vary periodically to produce a modulated electrical signal, whose frequency is proportional to the speed with which it changes magnetic field.

To obtain this change, a metal ring (the inside of the pulley) with a series of openings passes through the sensor. As it moves, the metal part of the ring covers the sensor, blocking the magnetic field, resulting in a low output signal; viceversa, level with the gap and so when the magnetic field is present, the sensor generate a high signal.

The alternating of the signals therefore depends on the succession of the openings.

1, Supply (+)

2, Signal output

3, Earth (-)

5, Deflector

6, Magnetic material

7, Gap

1.6 16v · BIPOWER, Euro 3

CONSTRUCTION FEATURES

The Marelli IAW 4EF.G1 system belongs to the category of systems integrated with:

• inductive discharge digital electronic ignition
• distributorless
• sequential, phased electronic injection (1-3-4-2).

1, Safety and ventilation valve

2, Fuel tank

3, Electric fuel pump

4, Idle speed actuator

5, Radiator fan high and low speed relay feeds

6, Battery

7, Ignition switch

8, Injection system relay

9, CODE control unit

10, Inertia switch

11, Vehicle speed sensor

12, Diagnostic socket

13, Rev counter

14, Injection system failure warning light

15, Fuses protecting injection/ignition system

16, General protective fuse box

17, Butterfly valve position sensor

18, Fuel supply manifold

19, Injectors

20, Air filter

21, Spark plugs

22, Ignition coils

23, Engine coolant temperature gauge

24, Air temperature and pressure sensor

25, Rpm and T.D.C. sensor

26, Detonation sensor

27, Coolant temperature sensor

28, Fuel vapour solenoid valve

29, Activated charcoal filter

30, Climate control compressor

31, Lambda sensor (precatalyzer)

32, Catalytic silencer

33, Injection-ignition control unit (petrol)

34, Multi-purpose valve

35, Engine coolant overheating warning light

36, Climate control compressor relay

37, Climate control system relay

38, Lambda sensor (post catalyzer)

39, Injection timing sensor

40, Methane engine management control unit

41, Petrol pump deactivation relay

OPERATION

The system is configured to normally run on methane.

It is possible to switch from methane to petrol:

• upon a manual control from the user, via the switching button located in the passenger compartment;
• automatically through the engine management electronic control unit if the methane in the tank has run out (pressure in the cylinder below 11 bar) or in recovery conditions when methane operation is not advisable.

In the first case, methane operation is reset by simply deactivating the button; In the second case, it takes place when the conditions that determined it cease (upon next key-on).

The engine is started up on methane. The engine is only started up on petrol after a complete refilling in order to ensure that the injectors are working properly and the system switches to methane operation after a few seconds. There must always therefore be petrol in the tank. For this reason the instrument panel contains both types of fuel gauge.

The Magneti Marelli IAW 4EF.G1 essentially manages the following functions:

• system self-adaptation
• self test
• recognition of FIAT CODE
• control of cold starting
• control of combustion - Lambda sensors
• control of detonation
• control of mixture enrichment during acceleration
• fuel cut-off during overrunning
• fuel vapour recovery
• limitation of the maximum rpm
• fuel supply check
• connection to the climate control system
• recognition of cylinder position
• regulation of fuel injection times
• adjustment of ignition advance values
• control and management of the idle speed
• control of electric cooling fan
• diagnosis of 'Fuel System'
• diagnosis of catalyzer
• diagnosis of Lambda sensors
• diagnosis of 'Misfire'
• communication with the Metatron METAFUEL 5D0.2B0 control unit via a high-speed CAN line that is used to exchange data, commands and other information.

The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

During idling, the control unit checks:

• the moment of ignition
• air flow

with the benefit of maintaining correct operation of the engine when the environmental parameters and the applied loads vary.

INJECTION SYSTEM

There are basically two essential conditions that must always be met in the preparation of the air/fuel mixture for the smooth operation of controlled ignition engines, namely:

• the 'metering' (air/fuel ratio) must constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the necessary rapidity of combustion, avoiding unnecessary fuel consumption
• the 'homogeneity' of the mixture, consisting of petrol vapours, diffused as finely and evenly as possible in the air.

The injection/ignition system uses an indirect measuring system known as the 'SPEED DENSITY-LAMBDA type, in other words the angular rotation speed, the density of the intake air and the control of the mixture strength (feed-back).

In practice the system uses data on the ENGINE SPEED (rpm) and AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.

The quantity of air drawn in by each cylinder, for each engine cycle depends not only on the density of the intake air, but also on the unit displacement and the volumetric efficiency.

The density of the air refers to that of the air drawn in by the engine and calculated according to the absolute pressure and the temperature, both detected in the inlet manifold by specific sensors.

Volumetric efficiency refers to the parameter relating to the coefficient for filling the cylinders measured on the basis of experimental tests carried out on the engine throughout the entire operating range and then stored in the electronic control unit memory.

Having established the quantity of intake air, the system has to provide the quantity of fuel according to the desired mixture strength.

The end of injection pulse or supply timing is contained in a map stored in the control unit memory and varies according to the engine speed and the pressure in the inlet manifold. In practice, it involves processing which the electronic control unit carries out to command the sequential, phased opening of the four injectors, one per cylinder, for the length of time strictly necessary to form the air/petrol mixture which is closest to the stoichiometric ratio.

The fuel is injected directly into the manifold near the inlet valve at a pressure of around 3 bar.

Whilst the speed (rpm) and the density of the air (pressure and temperature) are used to measure the quantity of intake air, which when established allows the quantity of fuel to be metered according to the desired mixture strength, the other sensors in the system (coolant temperature, throttle valve position, battery voltage, etc.) allow the electronic control unit to correct the basic strategy for all engine operating conditions.

It is vital for the air/fuel ratio to be around the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for the reduction of pollutant emissions.

The injection system operation and strategies are basically identical for both petrol and methane operation.

Ignition system

The ignition is of the inductive discharge type, breakerless with power modules located in the electronic injection/ignition control unit.

The system has two high tension twin outlet coils joined in a single container and connected directly to the spark plugs.

The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage) and to the pins for the electronic control unit for connection to earth.

After the starting stage, the electronic unit manages the basic advance taken from a special map according to the:

• engine rpm
• absolute pressure value (mmHg) measured in the inlet manifold.

This advance value is corrected according to the temperature of the engine coolant and the intake air.

The spark plugs for cylinder 1-4 and 2-3 are connected directly (two at a time) by means of high tension leads to the terminals of the coil secondary winding and their connection is in series because the cylinder head joins them. This solution is also known as the 'lost spark' becuse the energy accumulated by the coil is almost exclusively discharged at the electrodes for the spark plug of the cylinder under compression allowing the ignition of the mixture. The other spark is obviously not used, as no mixture is found in the cylinder to ignite, only exhaust gas.

DIAGRAM OF INPUT/OUTPUT INFORMATION TO/FROM THE CONTROL UNIT

Communication between the petrol engine control unit and the methane engine control unit takes place via the CAN line.

1, Electronic control unit

2, Speedometer sensor

3, CODE control unit

4, Engine idle speed actuator

5, Fuel injectors

6, Fuel vapour solenoid valve

7, Diagnostic socket

8, Spark plugs

9, Ignition coils

10, Engine coolant overheating warning light

11, Injection failure warning light

12, Climate control system

13, Engine coolant temperature sensor

14, Intake air temperature and pressure sensor

15, Butterfly valve position sensor

16, Detonation sensor

17, Rpm and TDC sensor

18, Injection timing sensor

19, Ignition switch

20, Lambda sensor (pre catalyzer)

21, Lambda sensor (post catalyzer)

22, Electric fuel pump

23, Radiator fan high and low speed relay feeds

24, Rev counter / speedometer

25, Methane engine management control unit

OPERATING STRATEGY

Self-adaptation of the system

The control unit has a self-adapation function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.

These changes are stored in the form of modifications to the basic mapping, and their purpose is to adapt the operation of the system to the gradual alterations in the engine and components compared with their characteristics when new.

This self-adaptation function also makes it possible to even out inevitable differences (due to production tolerances) in any replaced components.

From the exhaust gas analysis, the control unit changes the basic mapping in relation to the original characteristics of the new engine.

The self-adaptation parameters are not cancelled if the battery is disconnected.

Self-test

The control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram. This warning light signals both engine management faults and problems detected by the EOBD strategies.

The (MIL) warning light operating logic is as follows:

• with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The control unit's self-test system checks the signals coming from the sensors, comparing them with the permitted limits:

Signalling of faults during engine starting:

• the failure of the warning light to go out once the engine has been started up means that there is an error memorized in the control unit.

Fault indication during operation:

• the warning light flashing indicates possible damage to the catalyzer due to misfire.
• the warning light constantly on indicates the presence of engine management errors or EOBD errors.

Recovery

From time to time, the control unit defines the type of recovery according to the components which are faulty.

The recovery parameters are managed by those components which are not faulty.

1.6 16v · from 09/03 · BIPOWER, Euro 3

If significant faults are detected in the system's components (e.g. petrol injectors), the recovery logic permits emergency starting on methane; for further details Characteristic of working principle 1058 CNG FUEL SYSTEM.

1.6 16v · BIPOWER, Euro 3

Recognition of fiat code

When the control unit receives the ignition 'ON signal, it dialogues with the Fiat CODE control unit to obtain starting enablement.

Communication takes place via the dedicated bidirectional serial diagnostic line which connects the two control units.

Starting and post-starting

During starting it is not possible to instantly recognize the engine timing and consequently it is not possible to implement the timed injection for the first injection for each cylinder.

When the engine is first running an initial simultaneous (full-group) injection is carried out because the considerable fluctuations in the rotation speed do not allow the correct calculation of the injection stage; it is only later that the injection becomes phased.

The base pulse constant is increased by a multiplication coefficient for the entire time the engine is driven by the starter motor.

After starting, the coefficient is gradually reduced until it disappears within a certain period; the lower the engine temperature, the longer this period.

Combustion control - lambda sensors

In EOBD systems the Lambda sensors, which are all the same type, are located upstream of the catalyzer and downstream of the catalyzer. The upstream sensors carry out the check on the mixture strength known as the 1st loop (upstream sensor closed loop). The sensor downstream of the catalyzer is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters. With this in mind, the adjustment of the second loop is designed to recover both production differences and those in the response of the upstream sensors which may occur as a result of ageing and pollution. This control is known as the 2nd loop (downstream sensor closed loop).

Operation when cold

Under these circumstances there is a natural weakening of the mixture because of the poor turbulence of the fuel particles at low temperatures, reduced evaporation and condensation on the inner walls of the inlet manifold, all of which is exacerbated by the increased viscosity of the lubricant oil which, as is well known, increases the rolling torque of the engine mechanical components at low temperatures.

The electronic control unit recognizes this condition on the basis of the coolant temperature signal, increasing the basic injection time.

Whilst the engine is warming up, the electronic control unit also operates the stepping motor which determines the quantity of air needed to ensure that the engine does not cut out.

Operation under full load

Operation in full load conditions is detected, by the control unit, through the values supplied by the butterfly position and absolute pressure sensors.

In full load conditions, the basic injection time must be increased to obtain the maximum power supplied by the engine.

Operation during over-run

During this stage the engine has two strategies:

• A negative, transitory strategy to keep the quantity of fuel supplied to the engine at the stoichiometric value (less pollution). This stage is recognized by the control unit when the butterfly potentiometer signal goes from a high voltage reading to a lower one.
• A soft accompaniment strategy at the lower speed (dash-pot) to lessen the variation in the torque supplied (reduced engine braking).

Barometric correction

Atmospheric pressure varies according to the altitude creating a variation in the volumetric efficiency which requires correction of the basic mixture strength (injection time).

The correction of the injection time depends on the variation in altitude and is automatically updated by the electronic control unit each time the engine is switched off and in certain butterfly position and rpm conditions (typically at low speeds and with the butterfly wide open) (dynamic adjustment of barometric correction).

Operation during cut-off

The cut-off strategy is implemented when the control unit recognizes the throttle valve in the idle position (throttle potentiometer signal) and the engine speed exceeds 1350 rpm. The control unit only enables the cut-off when the engine temperature exceeds 0° C.

The recognition of the throttle valve in a non closed position or the engine speed below 1270 rpm enables the supply to the engine.

For very high speeds the cut-off is implemented even when the throttle is not completely closed, but when the pressure in the inlet manifold is particularly low (partial cut-off).

Operation during acceleration

During this stage, the control unit increases the quantity of fuel requested by the engine as appropriate (to achieve maximum torque) according to the signals coming from the following components:

• throttle potentiometer;
• rpm and T.D.C. sensor.

The base pulse constant is multiplied by a coefficient which depends on the temperature of the engine coolant, the opening speed of the accelerator throttle and the increase in pressure in the inlet manifold.

If the sharp variation in the injection time is calculated when the injector is already closed, the control unit reopens the injector (extra pulse) in order to compensate the mixture strength extremely quickly; the subsequent injections are already increased on the basis of the coefficients mentioned previously.

Protection against excess rpm

When the engine rotation speed exceeds 6700 rpm for more than 10 seconds or reaches the 'limit' of 6900 rpm, set by the manufacturer, the engine finds itself operating in 'critical' conditions.

When the electronic control unit recognizes that the above speed has been exceeded, it prevents the operation of the injectors.

When the rotation speed returns to a non critical value, the operation is resumed.

Petrol injector control

The operation of the injectors is the sequential, phased type. However, during starting the injectors are operated once in parallel (full-group).

The timing of the injector operation varies according to the engine speed and pressure of the inlet air in order to improve the filling of the cylinders with advantages in terms of consumption, driveability and pollution.

The injectors are electrically supplied by means of a specific twin relay: the engine management control unit closes the contacts for the section relating to the petrol injectors according to specific situations.

Control of detonation

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor. The strategy continuously compares the signal coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

If the system recognizes the presence of detonation, the strategy reduces the ignition advance until the phenomenon disappears. Later, the advance is gradually restored to the basic value or until the phenomenon occurs again. Later, the advance is gradually restored to the basic value or until the phenomenon occurs again.

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The strategy also features a self-adaptation function which temporarily memorizes the reductions in the advance that may be continuously repeated, in order to adjust the advance to the different engine operating conditions (for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to the threshold value memorized when the conditions which have caused the reduction no longer exist.

Management of radiator fan

The control unit directly controls the operation of the radiator fan according to the temperature of the engine coolant and the engagement of the climate control system.

The fan is switched on when the temperature exceeds 98°C (1^st speed) and 101° C (2^nd speed). The fan is switched off with a hysteresis of 2° C below the engagement threshold.

The high and low speed functions are managed by the intervention of special relays in the climate control system control unit and are operated by the control unit.

Engine idle management

The general aim of this strategy is to keep the engine idling at around the value memorized (engine warm: 850 rpm); the position of the actuator depends on the following engine conditions:

• Starting: when the key is inserted, the position of the actuator depends on the temperature of the engine coolant and the voltage of the battery (open-loop position).
• Warming up: the engine speed is corrected, particularly on the basis of the engine coolant temperature. With the engine at operating temperature, the management of the idle depends on the signal coming from the rpm sensor; when external loads are switched on, the control unit manages the supported idle.
• Deceleration stage: deceleration conditions outside of idling, the control unit controls the position of the engine idle speed actuator by means of a special flow rate curve (dash-pot curve), in other words it slows down the return of the shutter towards its seating, improving the engine braking effect.

Recognition of cylinder position

The engine timing signal, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognize the succession of cylinders to implement phased injection.

This signal is generated by a Hall-effect sensor, positioned on the cylinder head near the phonic wheel on the inlet camshaft.

Management of fuel (petrol) vapour recirculation

This strategy controls the position of the vapour cut out solenoid valve in the following way:

• during starting the solenoid remains closed, preventing the fuel vapours from enriching the mixture too much; this condition persists until the temperature of the coolant temperature reaches 65° C;
• with the engine at operating temperature, the electronic control unit sends the solenoid valve a square wave signal (duty-cycle operation) and the opening is modulated.

In this way the control unit controls the quantity of fuel vapours sent to the inlet, preventing considerable variations in the mixture strength.

In the conditions listed below, the operation of the solenoid valve is inhibited, maintaining the same in the closed position; this improves engine operation:

• throttle valve in closed position
• engine speed below 1500 rpm
• inlet manifold pressure below the limit calculated by the control unit depending on the number of revs,

Climate control system management

The injection/ignition control unit is connected to the climate control system in that:

• it receives the request to switch on the compressor and make the related interventions (additional air);
• it gives the go ahead to switch on the compressor, when the conditions covered by the strategies have arisen;
• it receives information on the state of the four-stage pressure switch and makes the appropriate interventions (radiator fan operation).

If the engine is idling, the control unit increases the flow rate of the air passing from the idle actuator before the compressor is switched on and, viceversa, it returns the actuator to the normal position after the compressor is switched off.

The control unit automatically controls the disengagement of the compressor:

• at engine coolant temperatures above a certain level
• at engine speeds below 750 rpm.

The control unit temporarily controls the disengagement of the compressor (for a few seconds):

• during high power requests from the engine (strong acceleration)
• during engine pickup.

Recovery

AIR TEMPERATURE SENSOR

If the error is present during starting:

• it assumes a value of 50 C
• self-adjustment of the mixture strength is inhibited.

If the error is present in other conditions:

• the last valid value is memorized and updated according to the coolant temperature.

DETONATION SENSOR

If the sensor is faulty, the engine control unit implements more conservative ignition advance 'maps' to safeguard the engine.

LAMBDA SENSORS

In the case of a failure, the information transmitted is ignored and the system operates in open-loop.

PRESSURE SENSOR

If the failure is present during starting, it uses a value of 1024 mbar. During operation the value used is calculated on the basis of parameters supplied by the throttle valve position sensor and the rpm sensor. The self-adjustment of the mixture strength is inhibited.

BUTTERFLY VALVE POSITION SENSOR

In the case of a fault, a value calculated from the absolute pressure sensor readings is set, and if this sensor is broken, a fixed value equal to a throttle opening of 50 degrees is set. The mixture strength and idle self-adjustment dash-pot strategies are suspended.

VEHICLE SPEED SENSOR

The control unit uses the last vehicle speed value memorized when there was no error.

COOLANT TEMPERATURE SENSOR

In the case of a failure the ECU inhibits the self-adjustment of the mixture strength and idle. It sets the last temperature value measured; if this does not correspond to the normal working value, the ECU increases it gradually according to the time since the engine was started up until it reaches 80 °C. The radiator cooling fan is operated

ENGINE IDLE SPEED ACTUATOR

In the event of a fault, the operation of the actuator is disabled and self-adjustment of the idle mixture strength is stopped.

IAW 49EF.G1INJECTION-IGNITION CONTROL UNIT

The engine unit is fitted in the engine compartment and is capable of withstanding high temperatures.

It is a digital type with a microprocessor, featuring a high calculation capacity, precision, reliability, versatility and low energy consumption and is maintenance-free.

The task of the electronic control unit is to process the signals coming from the various sensors through the application of software algorithms and control the operation of the actuators (in particular the injectors, ignition coils and idle actuator) in order to ensure optimum engine operation and communicate with the METAFUEL 5D0.2B0 control unit via a high-speed CAN line to exchange data, commands and other information.

The adoption of the Fiat CODE does not allow control units to be exchanged between cars.

Iaw 4ef.g1 control unit pin-out

The diagram below shows the control unit pins.

Connector A:

1, Pre-catalyzer Lambda sensor heater

2, Post-catalyzer Lambda sensor heater

3, Not connected

4, Rev counter signal

5, Not connected

6, CAN L

7, Not connected

8, Not connected

9, Pre converter Lambda sensor (negative)

10, Not connected

11, Not connected

12, Post converter Lambda sensor (positive)

13, Fiat CODE control unit two-way line

14, Radiator fan high speed relay control

15, Pump relay enablement

16, Not connected

17, Engine coolant overheating warning light

18, CAN line earth

19, Not connected

20, Pre catalyzer Lambda sensor (positive)

21, Radiator fan high speed request signal

22, Not connected

23, Fuel level signal

24, Postconverter lambda sensor (negative)

25, Diagnostic socket (line K)

26, Injection system failure warning light (EOBD)

27, Control unit earth

28, Control unit earth

29, Control unit supply (+30)

30, Not connected

31, Not connected

32, CAN H

33, Not connected

34, Not connected

35, Radiator fan low speed request signal

36, Not connected

37, Not connected

38, Not connected

39, Not connected

40, Radiator fan low speed relay control

41, Air conditioning compressor relay feed

42, Not connected

43, Not connected

44, Lambda sensors cable screening

45, Not connected

46, Not connected

47, Supply (+15)

48, Air conditioning engagement request

49, Relay control

50, Vehicle speed signal

51, Not connected

52, Fuel vapour solenoid valve

Connector B:

53, Rpm sensor (positive)

54, Sensor earth

55, Intake air temperature signal

56, Detonation sensor (positive)

57, Engine idle speed actuator

58, Engine idle speed actuator

59, Ignition coil control (cylinders 1-4)

60,Throttle position sensor supply

61, Not connected

62, Engine coolant temperature sensor (positive)

63, Detonation sensor cable shielding

64, Engine idle speed actuator

65, Engine idle speed actuator

66, Ignition coil control (cylinders 2-3)

67, Rpm sensor (negative)

68, Sensor supply (+5V)

69, Timing sensor signal

70, Detonation sensor (negative)

71, Cylinder 1 injector control

72, Cylinder 4 injector control

73, Not connected

74, Fuel consumption signal

75, Intake air pressure signal

76, Throttle position signal

77, Rpm sensor cables shielding

78, Cylinder 3 injector control

79, Cylinder 2 injector control

80, Not connected

PETROL INJECTORS

Construction features

The twin jet injectors (with the spray at an angle in relation to the injector axis) are specifically designed for engines with 4 valves per cylinder, making it possible to direct the jets towards the two inlet valves.

The injectors are fixed by the fuel manifold, which presses them into their seats in the inlet ducts. They are also secured to the fuel manifold by means of 'safety clips'. Two viton seals ensure a seal at the inlet manifold and the fuel manifold.

Operation

The jets of fuel, at a differential pressure of 3 bar, come out of the injector and are instantly atomized forming two cones.

The control logic for the injectors is the 'sequential phased type', in other words the four injectors are operated according to the inlet sequence of the engine's cylinders.

The methane injectors are described in chapter 1058.

PETROL MANIFOLD

The upper part is made from plastic whilst the lower part is produced by aluminium die-casting and incorporates the seats for the injectors.

The fuel manifold is fixed to the inner part of the inlet manifold and its function is to send the fuel to the injectors.

ENGINE COOLANT TEMPERATURE SENSOR

Construction features

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

One NTC thermistor sends the signal to the injection control unit whilst the other one sends the signal to the temperature gauge and warning light.

The sensor is based on semiconductor technology; so if the sensor temperature increases as the water temperature increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

1, Engine earth

2, Temperature gauge on instrument panel

3, Electrical connection

4, Motor metal casing

5, Engine earth

6, NTC for thermometer

7, NTC fuel injection

DETONATION SENSOR

Construction features

The piezoelectric type detonation sensor is fitted on the cylinder block/crankcase and detects the intensity of the vibrations caused by the detonation in the combustion chambers.

This phenomenon produces a mechanical repercussion on a piezoelectric crystal which sends a signal to the control unit; on the basis of this signal, the control unit reduces the ignition advance until the phenomenon has disappeared. The advance is then gradually restored to the basic value.

Operation

The molecules of a quartz crystal feature electrical polarization.

In rest conditions (A) the molecules do not have a particular direction.

When the crystal is subjected to pressure or an impact (B), they are directed - the higher the pressure to which the crystal is subjected, the more marked their direction. This direction produces a voltage at the ends of the crystal.

A. Rest position

B. Under pressure position

Electrical properties: resistance between pin 1 and pin 2: 560 ± 28 ohms

RPM SENSOR

Construction features

It is fitted on the cylinder block/crankcase and faces the phonic wheel on the crankshaft pulley.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the flywheel (60-2 teeth).

The fuel injection control unit uses the rpm sensor to:

• determine the speed of rotation
• determine the angle of the crankshaft.

Composition

The sensor consists of a tubular casing (1) which contains a permanent magnet (3) and an electrical winding (2).

Operation

As the flywheel teeth go past, the magnetic flow produced by the magnet (3) undergoes fluctuations due to the change in the gap.

These fluctuations induce an electromotive force in the winding (2), at the ends of which there is a voltage which alternates between positive (tooth opposite sensor) and negative (gap opposite sensor). The peak value of the output voltage from the sensor, provided other factors remain the same, depends on the distance between the sensor and tooth (gap).

The phonic wheel comprises sixty teeth, two of which have been removed to create a reference: the pitch of the wheel thus corresonds to an angle of 6 (360 divided by 60 teeth). The synchronization point is recognized at the end of the first tooth after the space created by the two missing teeth: when this passes under the sensor, the pair of pistons 1-4 of the engine are at 114 before TDC.

Electrical specifications: resistance: 11341386 ohms at 20C.

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.5 and 1.5 mm.

THROTTLE BODY

Construction features

This has the task of metering the amount of air supplied to the engine according to the request from the driver via the accelerator.

The butterfly is opened by means of a non linear linkage which, depending on the pedal travel, produces small butterfly opening angles in the first section of the accelerator pedal travel and, conversely, greater angles with the pedal very depressed.

With the pedal completely released, the additional air required is supplied by the engine idle speed actuator.

Under these circumstances, the butterfly opening lever is agains an anti-tamper screw which prevents the butterfly from getting stuck in the closed position.

To avoid condensation and the formation of ice which could occur in certain conditions when the outside temperature is very low and/or it is very damp, the throttle casing is heated with a small amount of coolant coming from the engine thermostat made to circulate in a chamber inside the actual casing.

The butterfly valve position sensor and the engine idle speed actuator are also fitted on the throttle body.

The anti-tamper screw is regulated during flushing operation in the factory and should never be tampered with.

TIMING SENSOR

Construction features

This system uses a sequential phased injection system, i.e. the fuel injection takes place in sequence for each cylinder at the intake stage.

To do this, in addition to the rpm and TDC signal, the electronic unit also uses another signal to determine the injection point. The signal sent to the control unit is produced by a Hall-effect sensor (2) mounted level with the inlet side camshaft drive pulley.

1, Fixing bolts

2, Hall-effect sensor

3, Inlet side camshaft pulley

Operation

A semiconducting layer, through which current passes, immersed in a perpendicular magnetic field (force lines perpendicular to the current direction), generates at its ends a difference in potential known as Hall voltage.

If the intensity of the current remains constant, the voltage generated only depends on the intensity of the magnetic field; the intensity of the field simply has to vary periodically to produce a modulated electrical signal, whose frequency is proportional to the speed with which it changes magnetic field.

To obtain this change, a metal ring (the inside of the pulley) with a series of openings passes through the sensor. As it moves, the metal part of the ring covers the sensor, blocking the magnetic field, resulting in a low output signal; viceversa, level with the gap and so when the magnetic field is present, the sensor generate a high signal.

The alternating of the signals therefore depends on the succession of the openings.

1, Supply (+)

2, Signal output

3, Earth (-)

5, Deflector

6, Magnetic material

7, Gap

BUTTERFLY VALVE POSITION SENSOR

Construction features

This sensor consists of a potentiometer where the moving part is controlled by the butterfly valve shaft.

Composition

The potentiometer is of linear type (single ramp); its main characteristics are:

• total mechanical travel: from 0 to 105
• effective electrical angle: 88 to 92
• Temperature operating range: -30C - +125C

Operation

During operation, the control unit provides the potentiometer with a 5 Volt supply. The parameter measured is the butterfly position from minimum to full opening for the management of the injection.

On the basis of the output voltage, the control unit recognizes the throttle valve opening condition and suitably corrects the mixture strength.

With the butterfly closed, an electrical voltage signal is sent to the control unit which recognizes the idle and cut-off conditions (distinguishing between them on the basis of the engine speed).

The sensor does not require any type of adjustment to its angular position because the control unit recognizes the butterfly fully closed or fully open conditions by means of self-adaptation algorithms.

The potentiometer is the single ramp type and does not need to be adjusted because the control unit programme learns the throttle idle position (0 - 950 mV). The fastening of the potentiometer to the throttle casing is the SNAP-IN type.

ENGINE IDLE SPEED ACTUATOR (STEPPING MOTOR)

Construction features

The actuator is mounted on the throttle body and is controlled by the fuel injection control unit.

• an electrical stepping motor with two windings in the stator and a rotor composed of two permanent magnet poles
• a screw-female screw type reduction gear which transforms the rotary motion into linear motion of the shutter.

1, Bearing

2, Nutscrew

3, Coils

4, Magnet

5, Screw

6, Anti-rotation splining

7, Shutter

The electrical stepper motor features a high degree of precision and rapid resolution (about 200 steps per second). The impulses sent by the electronic control unit to the engine are transformed from a rotary motion into a linear motion (about 0.04 mm/step) by means of a screw-female screw type mechanism, operating the shutter whose movements alter the section of the by-pass duct.

The constant value of the minimum air flow rate (Q0) is due o the flow under the butterfly valve which is regulated in production and guranteed by an anti-tamper plug.

The maximum flow rate (Q2) is guaranteed by the shutter in the fully retracted position (about 200 steps corresponding to 8.8 mm). The law shown in the graph below applies between these two air flow rate values.

Q, Air flow rate regulated by the actuator (variable)

Q0, Air flow rate escaping from the butterfly (constant)

Operation

In order to idle, i.e. with the butterfly (4) completely closed, the engine requires a certain amount of air (Qo) and fuel to overcome the internal friction and sustain its rotation speed.

To the quantity of air (Qo) arriving from the filter which, during idling, flows through the throttle valve (4) in a closed position, it is necessary to add, when the engine is warming up or when electrical consumers are switched on or outside loads applied (air conditioning etc.), a further quantity of air (Q) to allow the engine to keep the rotation speed constant.

To achieve this result the system uses a stepping motor operated by a circuit inside the injection/ignition electronic control unit which, when operating, moves a rod fitted with a plunger which alters the section of the by-pass duct and, consequently, the quantity of air (Q0 + Q) drawn in by the engine.

To adjust this type of action, the electronic unit uses the engine angular speed and coolant temperature parameters, coming from the respective sensors.

The fastening for the stepping motor on the throttle casing is the SNAP-IN type.

INTAKE AIR TEMPERATURE AND PRESSURE SENSOR

Construction features

It is fitted on the inlet manifold and is an integrated component which has the task of measuring the pressure and the temperature of the air inside the inlet manifold. Both pieces of information are used by the injection control unit to define the quantity of air drawn in by the engine. This information is then used to calculate the injection time and the point of ignition.

Operation

Air temperature sensor

The air temperature sensor consists of an NTC thermistor (Negative Temperature Coefficient). The resistance of the sensor decreases as the temperature increases. The control unit input circuit divides the 5 Volt reference voltage between the sensor resistance and a fixed reference value, obtaining a voltage which is proportional to the resistance and therefore to the temperature.

(*) control temperature

Pressure sensor

The sensitive element of the pressure sensor consists of a Wheatstone bridge on a ceramic diaphragm. On one side of the diaphragm is the absolute reference vacuum, whilst on the other side there is the vacuum from the inlet manifold. The (piezoresistive) signal from the distortion suffered by the diaphragm, before being sent to the engine control unit, is amplified by an electronic circuit in the support which also houses the ceramic diaphragm. When the engine is off, the diaphragm bends in accordance with the atmospheric pressure; the altitude information is thus obtained.

When the engine is running, the effect of the vacuum produces a mechanical action on the sensor diaphragm, which bends, altering the resistance value. Since the supply is kept rigorously constant (5V) by the control unit, altering the resistance alters the voltage output value.

STATIC IGNITION COIL WITH FOUR HIGH TENSION OUTPUTS

Construction features

The ignition coils are fixed by a bracket to the camshaft covers.

They are the closed magnetic circuit type with a core made from silicon steel with a thin gap containing both windings.

The windings are covered by a moulded plastic container and are insulated by embedding in an epoxy resin and quartz compound which gives them exceptional dielectric, mechanical and thermal properties enabling them to withstand high temperatures. The proximity of the primary winding to the magnetic core reduces the magnetic flow losses optimizing the coupling with the secondary winding.

1, High tension output for cylinder 1 spark plug

2, High tension output for cylinder 2 spark plug

3, High tension output for cylinder 3 spark plug

4, High tension output for cylinder 4 spark plug

5, Low tension socket for control unit connection

Wiring diagram

The ignition coil wiring diagram is shown below.

1, High tension output for cylinder 1 spark plug

2, High tension output for cylinder 2 spark plug

3, High tension output for cylinder 3 spark plug

4, High tension output for cylinder 4 spark plug

5, Low tension connector

5a, Control for cylinders 2 and 3

5b, Battery positive

5c, Control for cylinders 1 and 4

6, Gap

VEHICLE SPEED SENSOR

Construction features

This sensor is located at the differential output, by the left driveshaft joint and transmits the vehicle speed to the control unit: the signal is also used for the operation of the speedometer.

The sensor is the Hall effect type: it calculates the speed of the vehicle on the basis of the frequency of the impulses.

1.6 16v · Euro 3, GPOWER

CONSTRUCTION FEATURES

The Marelli IAW 4EF.G1 system belongs to the category of systems integrated with:

• inductive discharge digital electronic ignition
• static distribution
• sequential, phased electronic injection (1-3-4-2).

1, Safety and ventilation valve

2, Fuel tank

3, Electric fuel pump with level gauge

4, Idle speed actuator

5, Radiator fan high and low speed relay feeds

6, Battery

7, Ignition switch

8, Injection system relay

9, CODE control unit

10, Inertia switch

11, Vehicle speed sensor

12, Diagnostic socket

13, Rev counter

14, Injection system failure warning light

12, Injection/ignition system protective fuses

16, General protective fuse box

17, Throttle valve position sensor

18, Fuel supply manifold

19, Injectors

20, Air filter

21, Spark plugs

22, Ignition coils

23, Engine coolant temperature gauge

24, Air temperature and pressure sensor

25, Rpm and T.D.C. sensor

26, Detonation sensor

27, Coolant temperature sensor

28, Fuel vapour solenoid valve

29, Active charcoal filter

30, Climate control compressor

31, Lambda sensor (preconverter)

32, Catalytic silencer

33, Injection-ignition control unit (petrol)

34, Multi-purpose valve

35, Engine coolant overheating warning light

36, Climate control compressor relay

37, Climate control system activation button

38, Lambda sensor (post catalyzer)

39, Injection timing sensor

40, LPG engine control unit

41, Petrol pump deactivation relay

42, Four-stage pressure switch

OPERATION

During this operating mode, the system works in the same way as the basic system

The basic Magneti Marelli 4EF.G1 electronic unit does not change its behaviour and the system management strategies are as for the basic version.

The specific parts of the LPG system do not interfere with the basic system in any way.

The Magneti Marelli IAW 4EF.G1 essentially manages the following functions::

• system self-adaptation;
• self-test
• recovery
• recognition of FIAT CODE
• starting and post-starting;
• control of combustion - Lambda sensors
• operation when cold;
• operation under full load conditions;
• operation during over-run;
• operation in acceleration conditions;
• Protection against excess rpm
• petrol injector control
• control of detonation
• Management of radiator fan
• Management of the engine idle
• recognition of cylinder position
• Management of fuel (petrol) vapour recirculation
• Management of the climate control system
• communication with the Metatron METAFUEL 5D0 control unit by means of a high speed CAN line that is used to exchange data, commands and other information.

The control unit controls and manages fuel injection so that the stoichiometric ratio (air/fuel) is always at the optimum value.

During idling, the control unit checks:

• the ignition instant
• air flow

with the benefit of maintaining correct operation of the engine when the environmental parameters and the applied loads vary.

INJECTION SYSTEM

There are basically two essential conditions that must always be met in the preparation of the air/fuel mixture for the smooth operation of controlled ignition engines, namely:

• the 'metering' (air/fuel ratio) must constantly be kept as close as possible to the stoichiometric ratio, so as to ensure the necessary rapidity of combustion, avoiding unnecessary fuel consumption
• the 'homogeneity' of the mixture, consisting of petrol vapours, diffused as finely and evenly as possible in the air.

The injection/ignition system uses an indirect measuring system known as the 'SPEED DENSITY-LAMBDA type, in other words the angular rotation speed, the density of the intake air and the control of the mixture strength (feed-back).

In practice the system uses data on the ENGINE SPEED (rpm) and AIR DENSITY (pressure and temperature) to measure the quantity of air drawn in by the engine.

The quantity of air drawn in by each cylinder, for each engine cycle depends not only on the density of the intake air, but also on the unit displacement and the volumetric efficiency.

The density of the air refers to that of the air drawn in by the engine and calculated according to the absolute pressure and the temperature, both detected in the inlet manifold by specific sensors.

Volumetric efficiency refers to the parameter relating to the coefficient for filling the cylinders measured on the basis of experimental tests carried out on the engine throughout the entire operating range and then stored in the electronic control unit memory.

Having established the quantity of intake air, the system has to provide the quantity of fuel according to the desired mixture strength.

The end of injection pulse or supply timing is contained in a map stored in the control unit memory and varies according to the engine speed and the pressure in the inlet manifold. In practice, it involves processing which the electronic control unit carries out to command the sequential, phased opening of the four injectors, one per cylinder, for the length of time strictly necessary to form the air/petrol mixture which is closest to the stoichiometric ratio.

The fuel is injected directly into the manifold near the inlet valve at a pressure of around 3 bar.

Whilst the speed (rpm) and the density of the air (pressure and temperature) are used to measure the quantity of intake air, which when established allows the quantity of fuel to be metered according to the desired mixture strength, the other sensors in the system (coolant temperature, throttle valve position, battery voltage, etc.) allow the electronic control unit to correct the basic strategy for all engine operating conditions.

It is vital for the air/fuel ratio to be around the stoichiometric value for the correct and prolonged operation of the catalytic silencer and for the reduction of pollutant emissions.

The injection system operation and strategies are basically identical for both petrol and LPG operation.

IGNITION SYSTEM

The ignition is the inductive discharge type, i.e. without a high tension distributor, with power modules located in the electronic injection/ignition control unit.

The system has two high tension twin outlet coils joined in a single container and connected directly to the spark plugs.

The primary winding for each coil is connected to the power relay (thereby receiving the battery voltage) and to the pins for the electronic control unit for connection to earth.

After the starting stage, the electronic unit manages the basic advance taken from a special map according to the:

• engine rpm
• absolute pressure value (mmHg) measured in the inlet manifold.

This advance value is corrected according to the temperature of the engine coolant and the intake air.

The spark plugs for cylinder 1-4 and 2-3 are connected directly (two at a time) by means of high tension leads to the terminals of the coil secondary winding and their connection is in series because the cylinder head joins them. This solution is also known as the 'lost spark' becuse the energy accumulated by the coil is almost exclusively discharged at the electrodes for the spark plug of the cylinder under compression allowing the ignition of the mixture. The other spark is obviously not used, as no mixture is found in the cylinder to ignite, only exhaust gas.

DIAGRAM OF INPUT/OUTPUT INFORMATION FROM THE CONTROL UNIT

The petrol engine control unit and the LPG engine control unit communicate via CAN line

1, Electronic control unit

2, Speedometer sensor

3, CODE control unit

4, Engine idle speed actuator

5, Petrol injectors

6, Fuel vapour solenoid valve

7, Diagnostic socket

8, Spark plugs

9, Ignition coils

10, Engine coolant overheating warning light

11, Injection failure warning light

12, Climate control system

13, LPG engine control unit

14, Engine coolant temperature sensor

15, Petrol pump

16, Fuel pump cut-out relay

17, Battery

18, Pressure and intake air temperature sensor

19, Throttle valve position sensor

20, Detonation sensor

21, Rpm and TDC sensor

22, Injection timing sensor

23, Ignition switch

24, Lambda sensor (preconverter)

25, Lambda sensor (postconverter)

26, Radiator fan high and low speed relays

27, Petrol/LPG operating mode selector

28, Speedometer/mileometer

OPERATING STRATEGIES

Self-adaptation of the system

The control unit has a self-adaption function which recognizes changes in the engine which occur as a result of bedding-in and ageing processes of both components and the engine itself.

These changes are stored in the form of modifications to the basic mapping, and their purpose is to adapt the operation of the system to the gradual alterations in the engine and components compared with their characteristics when new.

This self-adaptation function also makes it possible to even out inevitable differences (due to production tolerances) in any replaced components.

From the exhaust gas analysis, the control unit changes the basic mapping in relation to the original characteristics of the new engine

The self-adaptation parameters are not cancelled if the battery is disconnected.

Self-diagnosis

The control unit autodiagnostic system controls the correct operation of the system and signals any faults by means of an (MIL) warning light in the instrument panel which has a standardized European colour and ideogram. This warning light indicates engine management faults

The (MIL) warning light operating logic is as follows:

• with the ignition key in the ON position, the warning light comes on and remains on until the engine has been started up. The control unit's self-test system checks the signals coming from the sensors, comparing them with the permitted limits:

Signalling of faults during engine starting:

• the failure of the warning light to go out once the engine has been started up means that there is an error memorized in the control unit.

Fault indication during operation

• the warning light on constantly indicates the presence of engine management errors.

Recovery

From time to time, the control unit defines the type of recovery according to the components which are faulty.

The recovery parameters are managed by those components which are not faulty.

Recognition of fiat code

When the control unit receives the ignition 'ON signal, it dialogues with the Fiat CODE control unit to obtain starting enablement.

Communication takes place via the dedicated bidirectional serial diagnostic line which connects the two control units.

Starting and post-starting

During starting it is not possible to instantly recognize the engine timing and consequently it is not possible to implement the timed injection for the first injection for each cylinder.

When the engine is first running an initial simultaneous (full-group) injection is carried out because the considerable fluctuations in the rotation speed do not allow the correct calculation of the injection stage; it is only later that the injection becomes phased.

The 'basic' injection time is increased by a multiplication coefficient for the entire time the engine is driven by the starter motor.

After starting, the coefficient is gradually reduced until it disappears within a certain period; the lower the engine temperature, the longer this period.

Combustion control - lambda sensors

In EOBD systems the Lambda sensors, which are all the same type, are located upstream of the catalyzer and downstream of the catalyzer. The upstream sensors carry out the check on the mixture strength known as the 1st loop (upstream sensor closed loop). The sensor downstream of the catalyzer is used for the catalyzer diagnosis and for finely modulating the 1st loop control parameters. With this in mind, the adjustment of the second loop is designed to recover both production differences and those in the response of the upstream sensors which may occur as a result of ageing and pollution. This control is known as the 2nd loop (downstream sensor closed loop).

Operation when cold

Under these circumstances there is a natural weakening of the mixture because of the poor turbulence of the fuel particles at low temperatures, reduced evaporation and condensation on the inner walls of the inlet manifold, all of which is exacerbated by the increased viscosity of the lubricant oil which, as is well known, increases the rolling torque of the engine mechanical components at low temperatures.

The electronic control unit recognizes this condition on the basis of the coolant temperature signal, increasing the basic injection time.

Whilst the engine is warming up, the electronic control unit also operates the stepping motor which determines the quantity of air needed to ensure that the engine does not cut out.

Operation in full load conditions

Operation in full load conditions is detected, by the control unit, through the values supplied by the throttle position and absolute pressure sensors.

In full load conditions, the basic injection time must be increased to obtain the maximum power supplied by the engine.

Operation in deceleration conditions

During this stage the engine has two strategies:

• A negative, transitory strategy to keep the quantity of fuel supplied to the engine at the stoichiometric value (less pollution). This stage is recognized by the control unit when the butterfly potentiometer signal goes from a high voltage reading to a lower one.
• A soft accompaniment strategy at the lower speed (dash-pot) to lessen the variation in the torque supplied (reduced engine braking).

Barometric correction

The atmospheric pressure varies according to the altitude creating a variation in the volumetric efficiency which requires the correction of the basic mixture strength (injection time).

The correction of the injection time depends on the variation in altitude and is automatically updated by the electronic control unit each time the engine is switched off and in certain throttle position and rpm conditions (typically at low speeds and with the throttle wide open) (dynamic adjustment of barometric correction).

Operation during cut-off

The cut-off strategy is implemented when the control unit recognizes the throttle valve in the idle position (throttle potentiometer signal) and the engine speed exceeds 1350 rpm. The control unit only enables the cut-off when the engine temperature exceeds 0° C.

The recognition of the throttle valve in a non closed position or the engine speed below 1270 rpm enables the supply to the engine.

For very high speeds the cut-off is implemented even when the throttle is not completely closed, but when the pressure in the inlet manifold is particularly low (partial cut-off).

Operation in acceleration conditions

During this stage, the control unit increases the quantity of fuel requested by the engine as appropriate (to achieve maximum torque) according to the signals coming from the following components:

• throttle potentiometer;
• rpm and T.D.C. sensor.

The 'basic' injection time is multiplied by a coefficient which depends on the temperature of the engine coolant, the opening speed of the accelerator throttle and the increase in pressure in the inlet manifold.

If the sharp variation in the injection time is calculated when the injector is already closed, the control unit reopens the injector (extra pulse) in order to compensate the mixture strength extremely quickly; the subsequent injections are already increased on the basis of the coefficients mentioned previously.

Protection against excess rpm

When the engine rotation speed exceeds 6700 rpm for more than 10 seconds or reaches the 'limit' of 6900 rpm, set by the manufacturer, the engine finds itself operating in 'critical' conditions.

When the electronic control unit recognizes that the above speed has been exceeded, it prevents the operation of the injectors.

When the rotation speed returns to a non critical value, the operation is resumed.

Petrol injector control

The operation of the injectors is the sequential, phased type. However, during starting the injectors are operated once in parallel (full-group).

The timing of the injector operation varies according to the engine speed and pressure of the inlet air in order to improve the filling of the cylinders with advantages in terms of consumption, driveability and pollution.

The injectors are supplied via a specific relay.

Control of knock

The control unit detects the presence of knocking by processing the signal coming from the relevant sensor. The strategy continuously compares the signal coming from the sensor with a threshold value, which, in turn, is continuously updated to take account of background noise and ageing of the engine.

If the system recognizes the presence of detonation, the strategy reduces the ignition advance until the phenomenon disappears. Later, the advance is gradually restored to the basic value or until the phenomenon occurs again. In particular, advance increases are implemented gradually, whilst reductions are implemented immediately.

Under acceleration conditions, a higher threshold is used to take account of the increased engine noise under such conditions.

The strategy also features a self-adaptation function which temporarily memorizes the reductions in the advance that may be continuously repeated, in order to adjust the advance to the different engine operating conditions (for example, the use of a low octane rating fuel). The strategy is capable of restoring the advance to the threshold value memorized when the conditions which have caused the reduction no longer exist.

Management of radiator fan

The control unit directly controls the operation of the radiator fan according to the temperature of the engine coolant and the engagement of the climate control system.

The fan is switched on when the temperature exceeds 98°C (1st speed) and 101°C (2nd speed). The switching off takes place with a hysteresis of 2°C below the engagement threshold.

The high and low speed functions are managed by the intervention of special relays in the climate control system control unit and are operated by the control unit.

Management of the engine idle

The general aim of this strategy is to keep the engine idling at around the value memorized (engine warm: 850 rpm); the position of the actuator depends on the following engine conditions:

• Starting: when the key is inserted, the position of the actuator depends on the temperature of the engine coolant and the voltage of the battery (open-loop position).
• Warming up: the engine speed is corrected, particularly on the basis of the engine coolant temperature. With the engine at operating temperature, the management of the idle depends on the signal coming from the rpm sensor. when external loads are switched on, the control unit manages the supported idle.
• Deceleration stage: deceleration conditions outside of idling, the control unit controls the position of the engine idle speed actuator by means of a special flow rate curve (dash-pot curve), in other words it slows down the return of the shutter towards its seating, improving the engine braking effect (fast idle).

Recognition of cylinder position

The engine timing signal, together with the engine rpm and top dead centre (TDC) signal, allows the control unit to recognize the succession of cylinders to implement phased injection.

This signal is generated by a Hall-effect sensor, positioned on the cylinder head near the phonic wheel on the inlet camshaft.

Management of fuel vapour recirculation (petrol)

This strategy controls the position of the vapour cut out solenoid valve in the following way:

• during starting the solenoid remains closed, preventing the fuel vapours from enriching the mixture too much; this condition persists until the temperature of the coolant temperature reaches 65° C;
• with the engine at operating temperature, the electronic control unit sends the solenoid valve a square wave signal (duty-cycle operation) and the opening is modulated.

In this way the control unit controls the quantity of fuel vapours sent to the inlet, preventing considerable variations in the mixture strength.

In the condition listed below, the operation of the solenoid valve is inhibited, maintaining the same in the closed position; this improves engine operation:

• throttle valve in closed position
• engine speed below 1500 rpm
• inlet manifold pressure below the limit calculated by the control unit depending on the number of revs,

Management of the climate control system

The injection/ignition control unit is connected to the climate control system in that:

• it receives the request to switch on the compressor and make the related interventions (additional air);
• it gives the go ahead to switch on the compressor, when the conditions covered by the strategies have arisen;
• it receives information on the state of the four stage pressure switch and makes the appropriate interventions (radiator fan operation).

If the engine is idling, the control unit increases the flow rate of the air passing from the idle actuator before the compressor is switched on and, viceversa, it returns the actuator to the normal position after the compressor is switched off.

The control unit automatically controls the disengagement of the compressor:

• at engine coolant temperatures above a certain level
• at engine speeds below 750 rpm.

The control unit temporarily controls the disengagement of the compressor (for a few seconds):

• during high power requests from the engine (strong acceleration)
• during engine pickup.

Recovery

AIR TEMPERATURE SENSOR

If the error is present during starting:

• it assumes a value of 50 °C
• self-adjustment of the mixture strength is inhibited.

If the error is present in other conditions:

• the last valid value is memorized and updated according to the coolant temperature.

KNOCK SENSOR

If the sensor is faulty, the engine control unit implements more conservative ignition advance 'maps' to safeguard the engine.

LAMBDA SENSORS

In the case of a failure, the information transmitted is ignored and the system operates in open-loop.

PRESSURE SENSOR

If the failure is present during starting, it uses a value of 1024 mbar. During operation the value used is calculated on the basis of parameters supplied by the throttle valve position sensor and the rpm sensor. The self-adjustment of the mixture strength is inhibited.

THROTTLE POSITION SENSOR

In the case of a fault, a value calculated from the absolute pressure sensor readings is set, and if this sensor is broken, a fixed value equal to a throttle opening of 50 degrees is set. The mixture strength and idle self-adjustment dash-pot strategies are suspended.

VEHICLE SPEED SENSOR

The control unit uses the last vehicle speed value memorized when there was no error.

COOLANT TEMPERATURE SENSOR

In the case of a failure the ECU inhibits the self-adjustment of the mixture strength and idle. It sets the last temperature value measured; If this does not correspond, the ECU increases it gradually according to the time since the engine was started up until it reaches 80 °C. The radiator cooling fan is operated.

ENGINE IDLE SPEED ACTUATOR

In the event of a fault, the operation of the actuator is disabled and self-adjustment of the idle mixture strength is stopped.

IAW 4EF.G1 INJECTION-IGNITION CONTROL UNIT

The engine unit is fitted in the engine compartment and is capable of withstanding high temperatures.

It is a digital type with a microprocessor, featuring a high calculation capacity, precision, reliability, versatility and low energy consumption and is maintenance-free.

The task of the electronic control unit is to process the signals coming from the various sensors through the application of software algorithms and control the operation of the actuators (in particular the injectors, ignition coils and idle actuator) in order to ensure optimum engine operation and communicate with the METAFUEL 5D0 control unit via a high-speed CAN line to exchange data, commands and other information.

The adoption of the Fiat CODE does not allow control units to be exchanged between cars.

Iaw 4ef.g1 control unit pin-out

METAFUEL 5D0 CONTROL UNIT PIN-OUT

1, Earth for pre catalyzer Lambda sensor heater

2, Earth for post catalyzer Lambda sensor heater

3, Not connected

4, Rev counter signal

5, Not connected

6, CAN L

7, Not connected

8, Not connected

9, Pre converter Lambda sensor (negative)

10, Not connected

11, Not connected

12, Post converter Lambda sensor (positive)

13, Fiat CODE control unit two-way line

14, Radiator fan high speed relay control

15, Pump relay enablement

16, Not connected

17, Engine coolant overheating warning light (where fitted)

18, CAN line earth

19, Not connected

20, Pre converter Lambda sensor (positive)

21, Radiator fan high speed request signal

22, Not connected

23, Fuel level signal

24, Postconverter lambda sensor (negative)

25, Diagnostic socket (line K)

26, Injection system failure warning light (EOBD)

27, Power control unit earth

28, Power control unit earth

29, Supply (+30) with fuse

30, Not connected

31, Not connected

32, CAN H

33, Not connected

34, Not connected

35, Radiator fan low speed request signal

36, Not connected

37, Not connected

38, Not connected

39, Not connected

43, Radiator fan low speed relay control

41, Air conditioning compressor relay

42, Not connected

43, Not connected

44, Lambda sensors cable screening

45, Not connected

46, Not connected

47, Supply (+15)

48, Air conditioning engagement request

49, Not connected

50, Vehicle speed signal

51, Not connected

52, Fuel vapour solenoid valve

53, Rpm sensor (positive)

54, Sensor earth

55, Intake temperature signal

56, Knock sensor (positive)

57, Engine idle speed actuator

58, Engine idle speed actuator

59, Ignition coil control (cylinders 1-4)

60, Butterfly position sensor supply

61, Not connected

62, Engine coolant temperature sensor

63, Detonation sensor cable screening

64, Engine idle speed actuator

65, Engine idle speed actuator

66, Ignition coil control (cylinders 2-3)

67, Rpm sensor (negative)

68, Sensor supply (+5V)

69, Timing sensor signal

70, Knock sensor (negative)

71, Cylinder 1 injector control

72, Cylinder 4 injector control

73, Not connected

73, Fuel consumption signal

75, Intake air pressure signal

76, Throttle position signal

77, Rpm sensor cables screening

78, Cylinder 3 injector control

78, Cylinder 2 injector control

80, Not connected

PETROL INJECTORS

Construction features

The twin jet injectors (with the spray at an angle in relation to the injector axis) are specifically designed for engines with 4 valves per cylinder, making it possible to direct the jets towards the two inlet valves.

The injectors are fixed by the fuel manifold, which presses them into their seats in the inlet ducts. They are also secured to the fuel manifold by means of 'safety clips'. Two viton seals ensure a seal at the inlet manifold and the fuel manifold.

Operation

The jets of fuel, at a differential pressure of 3 bar, come out of the injector and are instantly atomized forming two cones.

The control logic for the injectors is the 'sequential phased type', in other words the four injectors are operated according to the inlet sequence of the engine's cylinders.

The LPG injectors are described in chapter See subassembly 1057 LPG FUEL SYSTEM..

PETROL MANIFOLD

The upper part is made from plastic whilst the lower part is produced by aluminium die-casting and incorporates the seats for the injectors.

The fuel manifold is fixed to the inner part of the inlet manifold and its function is to send the fuel to the injectors.

ENGINE COOLANT TEMPERATURE SENSOR

Construction features

It is fitted on the thermostatic cup and measures the temperature of the coolant by means of an NTC thermistor which has a negative resistance coefficient.

One NTC thermistor sends the signal to the injection control unit whilst the other one sends the signal to the temperature gauge and warning light.

The sensor is based on semiconductor technology; so if the sensor temperature increases as the water temperature increases, the resistance decreases.

As the variation in resistance is not linear, for the same temperature increment, it is higher for low temperatures than for high temperatures.

1, Engine earth

2, Temperature gauge on instrument panel

3, Electrical connection

4, Motor metal casing

5, Engine earth

6, NTC for thermometer

7, NTC fuel injection

KNOCK SENSOR

Construction features

The piezoelectric type detonation sensor is fitted on the cylinder block/crankcase and detects the intensity of the vibrations caused by the detonation in the combustion chambers.

This phenomenon produces a mechanical repercussion on a piezoelectric crystal which sends a signal to the control unit; on the basis of this signal, the control unit reduces the ignition advance until the phenomenon has disappeared. The advance is then gradually restored to the basic value.

Operation

The molecules of a quartz crystal are electrically polarised.

In rest conditions (A) the molecules do not have a particular direction.

When the crystal is subjected to pressure or an impact (B), they are directed - the higher the pressure to which the crystal is subjected, the more marked their direction. This direction produces a voltage at the ends of the crystal.

A. Rest position

B. Under pressure position

Electrical properties: resistance between pin 1 and pin 2: 560 ± 28 ohm.

1, Earth (-)

2, Power supply (+)

3, Connector seen from contact side

RPM SENSOR

Construction features

It is fitted on the cylinder block/crankcase and 'faces' the phonic wheel on the crankshaft pulley.

It is of the inductive type, i.e. it functions by means of the variation in the magnetic field generated by the passage of the teeth of the flywheel (60-2 teeth).

The fuel injection control unit uses the rpm sensor to:

• determine the speed of rotation
• determine the angle of the crankshaft.

Composition

The sensor consists of a tubular casing (1) which contains a permanent magnet (3) and an electrical winding (2).

Operation

As the flywheel teeth go past, the magnetic flow produced by the magnet (3) undergoes fluctuations due to the change in the gap.

These fluctuations induce an electromotive force in the winding (2), at the ends of which there is a voltage which alternates between positive (tooth opposite sensor) and negative (gap opposite sensor). The peak value of the output voltage from the sensor, provided other factors remain the same, depends on the distance between the sensor and tooth (gap).

The phonic wheel comprises sixty teeth, two of which have been removed to create a reference: the pitch of the wheel thus corresponds to an angle of 6° (360° divided by 60 teeth). The synchronization point is recognized at the end of the first tooth after the space created by the two missing teeth: when this passes under the sensor, the pair of pistons 1-4 of the engine are at 114° before TDC.

Electrical specifications: resistance:1134-1386 ohm at 20°C.

The distance (gap) for obtaining correct signals, between the end of the sensor and the flywheel, should be between 0.5 and 1.5 mm.

1, Sensor

2, Output signal

3, Signal corresponding to the two missing teeth

4, Crankshaft pulley with flywheel

THROTTLE BODY

Construction features

This has the task of metering the amount of air supplied to the engine according to the request from the driver via the accelerator.

The throttle is opened by means of non linear linkage which, depending on the accelerator pedal travel, produces small throttle opening angles in the first section of the pedal travel and, conversely, greater angles with the pedal very depressed.

With the pedal completely released, the additional air required is supplied by the idle speed actuator.

Under these circumstances, the throttle opening lever comes up against an anti-tamper screw which prevents the throttle from getting stuck in the closed position.

To avoid condensation and the formation of ice which could occur in certain conditions when the outside temperature is very low and/or it is very damp, the throttle casing is heated with a small amount of coolant coming from the engine thermostat made to circulate in a chamber inside the actual casing.

The throttle position sensor and the engine idle speed actuator are also fitted on the throttle body.

The anti-tamper screw is regulated during the fluxing operation in the factory and should never be tampered with.

TIMING SENSOR

Construction features

This system uses a sequential phased injection system, i.e. the fuel injection takes place in sequence for each cylinder at the intake stage.

To do this, in addition to the rpm and TDC signal, the electronic unit also uses another signal to determine the injection point. The signal sent to the control unit is produced by a Hall-effect sensor (2) mounted level with the inlet side camshaft drive pulley.

1, Fixing bolts

2, Hall-effect sensor

3, Inlet side camshaft pulley

Operation

A semiconducting layer, through which current passes, immersed in a perpendicular magnetic field (force lines perpendicular to the current direction), generates at its ends a difference in potential known as Hall voltage.

If the intensity of the current remains constant, the voltage generated only depends on the intensity of the magnetic field; the intensity of the field simply has to vary periodically to produce a modulated electrical signal, whose frequency is proportional to the speed with which it changes magnetic field.

To obtain this change, a metal ring (the inside of the pulley) with a series of openings passes through the sensor. As it moves, the metal part of the ring covers the sensor, blocking the magnetic field, resulting in a low output signal; viceversa, level with the gap and so when the magnetic field is present, the sensor generate a high signal.

The alternating of the signals therefore depends on the succession of the openings.

1, Supply (+)

2, Signal output

3, Earth (-)

4, Connector seen from contact side

5, Deflector

6, Magnetic material

7, Gap

8, Metal ring

THROTTLE POSITION SENSOR

Construction features

This sensor consists of a potentiometer where the moving part is controlled by the throttle valve spindle.

Composition

The potentiometer is of linear type (single ramp); its main characteristics are:

• total mechanical travel: from 0° to 105°
• effective electrical angle: from 88° to 92°
• temperature operating range: from -30°C to +125°C.

Operation

During operation, the control unit provides the potentiometer with a 5 Volt supply. The parameter measured is the throttle position from minimum to full opening for management of injection.

On the basis of the output voltage, the control unit recognizes the throttle valve opening condition and suitably corrects the mixture strength.

With the throttle closed, an electrical voltage signal is sent to the control unit which recognizes the idle and cut-off conditions (distinguishing between them on the basis of the engine speed).

The sensor does not require any sort of adjustment to its angular position because it is the control unit which, by means of suitable self-adjustment algorithms, recognizes that the throttle is fully closed or fully open.

The potentiometer is the single ramp type and does not need to be adjusted because the control unit programme learns the throttle idle position (0 - 950 mV). The fastening of the potentiometer to the throttle casing is the SNAP-IN type.

ENGINE IDLE SPEED ACTUATOR (STEPPING MOTOR)

Construction features

The actuator is fitted on the throttle casing and consists of:

• an electrical stepping motor with two windings in the stator and a rotor composed of two permanent magnet poles
• a screw-female screw type reduction gear which transforms the rotary motion into linear motion of the shutter.

1, Bearing

2, Nutscrew

3, Coils

4, Magnet

5, Screw

6, Anti-rotation splining

7, Shutter

The electrical stepper motor features a high degree of precision and rapid resolution (about 200 steps per second). The impulses sent by the electronic control unit to the engine are transformed from a rotary motion into a linear motion (about 0.04 mm/step) by means of a screw-female screw type mechanism, operating the shutter whose movements alter the section of the by-pass duct.

The constant value of the minimum air flow rate (Q0) is due to the flow under the throttle valve which is regulated in production and guaranteed by an anti-tamper plug.

The maximum flow rate (Q2) is guaranteed by the shutter in the fully retracted position (about 200 steps corresponding to 8.8 mm). The law shown in the graph below applies between these two air flow rate values.

Q, Air flow rate regulated by the actuator (variable)

Q0, Air flow rate escaping from the throttle (constant)

Operation

In order to idle, i.e. with the butterfly (4) completely closed, the engine requires a certain amount of air (Qo) and fuel to overcome the internal friction and sustain its rotation speed.

To the quantity of air (Qo) arriving from the filter which, during idling, flows through the throttle valve (4) in a closed position, it is necessary to add, when the engine is warming up or when electrical consumers are switched on or outside loads applied (air conditioning etc.), a further quantity of air (Q) to allow the engine to keep the rotation speed constant.

To achieve this result the system uses a stepping motor operated by a circuit inside the injection/ignition electronic control unit which, when operating, moves a rod fitted with a plunger which alters the section of the by-pass duct and, consequently, the quantity of air (Q0 + Q) drawn in by the engine.

To adjust this type of action, the electronic unit uses the engine angular speed and coolant temperature parameters, coming from the respective sensors.

The fastening for the stepping motor on the throttle casing is the SNAP-IN type.

INTAKE AIR TEMPERATURE AND PRESSURE SENSOR

Construction features

The sensor is fitted on the inlet manifold and is a built-in component. It records pressure and temperature inside the intake manifold. Both pieces of information are used by the injection control unit to define the quantity of air drawn in by the engine. This information is then used to calculate the injection time and the point of ignition.

Operation

Air temperature sensor

The air temperature sensor consists of an NTC thermistor (Negative Temperature Coefficient). The resistance of the sensor decreases as the temperature increases. The control unit input circuit divides the 5 Volt reference voltage between the sensor resistance and a fixed reference value, obtaining a voltage which is proportional to the resistance and therefore to the temperature.

(*) control temperature

Pressure sensor

The sensitive element of the pressure sensor consists of a Wheatstone bridge on a ceramic diaphragm. On one side of the diaphgram is the absolute reference vacuum, whilst the vacuum from the inlet manifold acts on the other side. The (piezoresistive) signal from the distortion suffered by the diaphgram, before being sent to the engine control unit, is amplified by an electronic circuit in the support which also houses the ceramic diaphragm. When the engine is off, the diaphragm bends in accordance with the atmospheric pressure; the altitude information is thus obtained.

When the engine is running, the effect of the vacuum produces a mechanical action on the sensor diaphragm, which bends, altering the resistance value. Since the supply is kept rigorously constant (5V) by the control unit, altering the resistance alters the voltage output value.

STATIC IGNITION COIL WITH FOUR HIGH TENSION OUTPUTS

Construction features

The ignition coils are fixed by a bracket to the camshaft covers.

They are the closed magnetic circuit type with a core made from silicon steel with a thin gap containing both windings.

The windings are covered by a moulded plastic container and are insulated by embedding in an epoxy resin and quartz compound which gives them exceptional dielectric, mechanical and thermal properties enabling them to withstand high temperatures. The proximity of the primary winding to the magnetic core reduces the magnetic flow losses optimizing the coupling with the secondary winding.

1, High tension output for cylinder 1 spark plug

2, High tension output for cylinder 2 spark plug

3, HIgh tension output for cylinder 3 spark plug

4, High tension output for cylinder 4 spark plug

5, Low voltage input for control unit connection, viewed from contact side.

5a, Control for cylinders 2 and 3

5b, Battery positive

5c, Control for cylinders 1 and 4

Wiring diagram

The ignition coil wiring diagram is shown below.

1, High tension output for cylinder 1 spark plug

2, High tension output for cylinder 2 spark plug

3, HIgh tension output for cylinder 3 spark plug

4, High tension output for cylinder 4 spark plug

5, Low tension connector

5a, Control for cylinders 2 and 3

5b, Battery positive

5c, Control for cylinders 1 and 4

6, Gap

VEHICLE SPEED SENSOR

Construction features

This sensor is located at the differential output, by the left driveshaft joint and transmits the vehicle speed to the control unit: the signal is also used for the operation of the speedometer.

The sensor is the Hall effect type: it calculates the speed of the vehicle on the basis of the frequency of the impulses.