Fuel Pump: Description and Operation

Fuel Pump Assembly:

The fuel pump used is a positive displacement, immersible gerotor pump with a permanent magnet electric motor. Fuel is drawn into the pump through the inlet screen at the end of the input tube, and pushed through the electric motor to the outlet. The pump contains a pair of check valves. The first check valve relieves internal fuel pump pressure, and regulates maximum pump output, by bleeding off excess pump output pressure back into the fuel tank. The second check valve mounted near the pump outlet line restricts fuel movement in either direction when the pump is not operating. This check valve maintains fuel pressure in the fuel supply line when engine is turned off. Fuel pump voltage is supplied through the Auto Shutdown (ASD) relay.

The fuel pump is mounted inside the module assembly. The fuel pump module assembly consists of the fuel pump, reservoir body, and fuel gauge sending unit. The reservoir body is used in place of the in-tank reservoir, and its main purpose is to ensure that there is fuel present at the fuel pump intake under all driving conditions. The fuel gauge sending unit is mounted to the side of the fuel pump assembly.

The fuel pumps maximum output pressure is 135 psi (930 kPa) and the fuel system pressure is regulated to approximately 48 psi (330 kPa), even when the vehicle is not operating. Fuel pressure must be released prior to servicing the fuel pump, fuel tank, fuel lines, fuel injectors, fuel filter, fuel gauge sending unit, or the fuel rail.