Fuel Pump: Description and Operation

Fuel Pump, Electric


The fuel system has a fuel pump relay controlled by the powertrain control module (PCM), which provides power to the fuel pump module under various operating conditions.

- When the ignition switch is in the OFF position:

- The contacts of the powertrain control module (PCM) power relay and the fuel pump relay are open. Both the PCM power relay and the fuel pump relay are contained within the power distribution box in the engine compartment.

- When the ignition switch is turned to the RUN position:

- The PCM power relay is energized. The PCM power relay provides power to the PCM and the fuel pump relay.
- The fuel pump will operate for one to three seconds or until the PCM receives crankshaft position signals. If the PCM does not receive crankshaft position signals indicating that the engine is turning over, the fuel pump is shut off. After the engine starts, the PCM will continue to operate the fuel pump as long as CKP signal are received.
- Power for the fuel pump is supplied through a high current fuse. Current flows through the fuel pump relay and inertia fuel shutoff (IFS) switch to the fuel pump.
- The IFS is a safety device designed to shut off the fuel pump in the event of a collision. If the IFS is tripped, the fuel system must be inspected for leaks before the IFS is reset.

The fuel system uses a fuel pump module. The fuel tank has an internal reservoir in which the fuel pump module resets. This design increases satisfactory pump operation during extreme vehicle maneuvers and steep inclines with low fuel levels.

The fuel pump module is mounted on the fuel tank. This assembly includes a check valve which is inside the fuel pump module rests. This design increases satisfactory pump operation during extreme vehicle maneuvers and steep inclines with low fuel levels.

The fuel pump module is mounted on the fuel tank. This assembly includes a check valve which is inside the fuel pump module outlet. The function of this valve is to maintain pressure in the system after the vehicle is shut down.

The pressure retention helps prevent hot starting concerns.

The fuel pump module has an internal pressure relief valve to provide overpressure protection in the event the fuel flow becomes restricted (damaged lines, clogged, filter, etc). Overpressure is restricted to 850 kPa (123 psi) and reduced fuel flow will result. The system pressure is controlled by the fuel pressure regulator mounted on the engine.

The fuel pump module is protected at its inlet by a nylon pick-up screen. It filters dirt and contaminants which could plug or damage the internal fuel pump module components, while at the same time allowing passage of small quantities of water which may have accumulated within the fuel tank reservoir.