Fuel Pump: Description and Operation

Roller Vane Fuel Pump - Exploded View:

Fuel Sender Assembly:

Fuel Sender Replacement:

DESCRIPTION
Two electric high pressure roller vane fuel pumps are attached to the fuel level meter assembly. The primary pump is in operation whenever the engine is running. The secondary pump is used only during cold cranking and operation, and during periods of secondary injector operation. A sump in the tank, located beneath the fuel pumps, assures a constant supply of fuel to both pumps even during low fuel conditions and aggressive vehicle maneuvers.

The electric fuel pumps are controlled by the ECM through individual fuel pump relays. When operating normally, the fuel pumps deliver more fuel than the engine can consume even at wide open throttle/full load. Excess fuel flows through the pressure regulator and back to the tank via the return line. The constant flow of fuel means that the fuel system is always supplied with cool fuel, thereby preventing the formation of fuel vapor bubbles in the fuel rail or injectors.