Fuel Pump Module - Operation

OPERATION - FUEL PUMP MODULE


An electric fuel pump is located within the primary fuel pump module. The electric fuel pump is a positive displacement, immersible pump with a permanent magnet electric motor capable of creating 860 kPa (125 psi) of operating pressure. The fuel pressure regulator limits fuel pressure to 400 kPa (58 psi).

On All Wheel Drive (AWD) vehicles, fuel is constantly being siphoned from the secondary side of the fuel tank to the primary side of the fuel tank whenever the fuel pump is operating. This is accomplished within the primary fuel pump module by diverting fuel from the electric fuel pump through the venturi jet pump creating a vacuum that pulls fuel from the secondary fuel pump module through the fuel transfer line and into the primary fuel module reservoir. When the secondary side of the fuel tank is empty, the venturi jet pump continues to fill the primary fuel pump reservoir with fuel from the primary side of the fuel tank.

All Wheel Drive (AWD) vehicles have two fuel level senders, the fuel gauge reading is an averaged of these two sensors. When diagnosing a sender concern the secondary fuel pump module reading should never be higher than the primary fuel pump module reading. It is possible, depending on fuel level and driving habits before diagnosing, to spill fuel over to the secondary side that might indeed show a lower resistance value than the primary side.

The fuel gauge is controlled by the instrument cluster circuit board based upon cluster programming and a hard wired input received by the cluster from the fuel level sending units on the modules in the fuel tank.

The instrument cluster continually monitors the fuel tank sending units to determine the level of fuel in the fuel tank. This information is available to other vehicle control modules via the Controller Area Network (CAN) data bus. Fuel gauge diagnosis is conducted as part of the instrument cluster circuitry.