310-01B Fuel Tank And Lines- 4.4L: Description And Operation (page 7 of 10)

Fuel Pressure Regulator 

The fuel pressure regulator is located in the manifold inside the fuel tank. The regulator controls the fuel pressure in the 
feed pipe to the fuel rail by allowing some fuel to be diverted to the front jet pump. 
 
The regulator is subject to pump output pressure and controls the pressure of the fuel delivered to the fuel rail to a 4.5 bar 
(65.2 lbf/in

2

). At pressures above this figure, the regulator opens, decaying the pressure supplied to the fuel rail by 

allowing fuel to pass to the front jet pump. The regulator is required to maintain the fuel pressure at the optimum pressure 
for correct fuel injection. 
 

Swirl Pot 

The swirl pot is located at the rear of the fuel tank and provides for the attachment or location of most of the fuel pump 
assembly components. 
 
The swirl pot acts as a fuel reserve, providing a constant supply of fuel to the fuel pump irrespective of fuel quantity or 
vehicle attitude. When the vehicle is level the swirl pot contains approximately 400 cm

3

 (24.4 in

3

) of fuel when the engine 

is running. The two jet pumps ensure that fuel is constantly supplied to the swirl pot to provide a sufficient fuel supply for 
the pump. 
 
A one way valve is located in the base of the swirl pot. The valve allows fuel from the tank to enter the swirl pot, but 
prevents it from escaping. 
 

Jet Pumps 

The fuel system incorporates two jet pumps. The front jet pump is located on the carrier near the front of the fuel tank. 
The rear jet pump is located in the swirl pot below the fuel pump. Both jet pumps operate on a venturi effect created by 
the fuel at pump output pressure passing through the jet pump. This draws additional fuel from the tank through ports in 
the jet pump body, delivering additional fuel to the swirl pot. 
 
The front jet pump is mainly used when the vehicle is driving downhill. The jet pump is connected via a pipe from the fuel 
manifold and receives fuel diverted from the fuel feed pipe by the pressure regulator. The front jet pump collects fuel from 
the front of the tank and transfers it into the swirl pot, ensuring a constant supply of fuel to the pump. The jet pump has a 
jet nozzle of 2.1 mm diameter. 
 
The rear jet pump operates at pump output pressure and delivers some of the fuel at pump pressure from the rear of the 
tank. 
 

Roll Over Valves (ROVs) 

Four ROVs are located on the carrier and are connected via pipes to a liquid vapour separator. The separator, which is 
also attached to the carrier, is connected via a pipe to the tank breather outlet in the pump module flange. The ROVs 
contain non-return valves which close in the event of the vehicle overturning, preventing liquid fuel escaping from the tank 
via the breather pipe. 
 

FUEL FILLER PIPE ASSEMBLY 

Fuel Filler - ROW