Fuel Pump: Description and Operation

Fig 1 Fuel Pump Module:

The fuel pump module is installed in the top of the fuel tank (Fig. 1). The fuel pump module contains the following:
- Electric fuel pump
- Fuel pump reservoir
- Inlet strainer
- Fuel pressure regulator
- Fuel gauge sending unit
- Fuel supply line connection

The inlet strainer, fuel pressure regulator and fuel level sensor are the only serviceable items. If the fuel pump requires service, replace the fuel pump module.

Operation
PCM controls the fuel pump through the fuel pump relay ground.

- When the key is in START or RUN position and the PCM is receiving an ignition reference signal, the PCM grounds the fuel pump relay, activating pump.

- If no ignition signal is sensed by the PCM, the PCM interrupts relay ground, turning pump off.

The electric fuel pump is located in and is part of the fuel pump module. It is a positive displacement, roller vane, immersible pump with a permanent magnet electric motor. The fuel pump module is suspended in fuel in the fuel tank. The pump draws fuel through a strainer and pushes it through the motor to the outlet. The pump 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 relay provides voltage to the fuel pump.

The fuel pump has a maximum deadheaded pressure output of approximately 635 kPa (95 psi). The regulator adjusts fuel system pressure to approximately 338 kPa (49 psi).