Fuel Pump Module - Operation

OPERATION

FWD





The front wheel drive (FWD) fuel pump module is located inside the fuel tank with a fuel level sending unit and pressure regulator. The fuel pump module is a positive displacement, gerotor, driven by a 12 volt DC permanent magnet electric motor.

The fuel pump module draws fuel through a internal filter and pushes it through the motor to an outlet pipe. The fuel pump module contains two check valves. One valve relieves internal fuel pump pressure and regulates maximum pump output. The second valve, in the pump outlet, maintains pump pressure during engine off conditions.

The fuel pump pressure regulator contains a calibrated spring which forces a diaphragm against the fuel filter return port. When pressure exceeds the calibrated amount, the diaphragm retracts, allowing excess fuel pressure in the fuel pump module to purge into the fuel tank.

The maximum deadhead pressure is approximately 880 kPa (130 psi). The fuel pump pressure regulator adjusts fuel system pressure to approximately 400 ± 34 kPa (58 ± 5 psi).

AWD





Operation of the all wheel drive (AWD) main fuel pump module is similar to the FWD with the addition of a auxiliary fuel pump module with a auxiliary fuel level sending unit and draws fuel from the base of the auxiliary fuel pump module (2) through an internal tube.

The auxiliary fuel pump module flow rate is greater than the vehicle fuel consumption rate so that the auxiliary side of the tank is emptied before fuel is depleted from the primary side.