Fuel Pump: Description and Operation

Fuel Sender Assembly:

90 Ohm Rheostat:

FUEL SENDER ASSEMBLY

The fuel sender assembly is attached to the top of the tank, and extends from the top of the tank to the sump, located in the bottom of the fuel tank.

The fuel sender assembly consists of the following major components: a fuel sender, fuel pump, and fuel pump strainer.

Fuel Sender

The fuel sender consists of the float, wire float arm, rheostat and the roll-over valve. Fuel level is sensed by the position of the float and float arm which operate the 90 ohm rheostat. As the float position changes, the amount of current passing through the rheostat varies, thus changing the gage reading on the instrument panel.

The roll-over valve is pressed into the vapor tube of the fuel sender and is not serviced separately. The roll-over valve prevents fuel from entering the engine compartment if the vehicle rolls over by shutting "OFF" the vapor pipe to the evaporative emission canister.

Fuel Pump

A high pressure turbine pump is mounted to the fuel sender inside the fuel tank. The fuel is pumped to the engine at a specified flow and pressure through the fuel pump. Excess fuel is returned to the fuel tank by a return line. The fuel pump delivers a constant flow of fuel to the engine even during low fuel conditions and aggressive vehicle maneuvers.

The electric fuel pump operation is controlled by the Powertrain Control Module PCM) through a fuel pump relay.

Fuel Pump Strainer

A woven plastic fuel pump strainer is attached to the lower end of the fuel pump in the fuel tank. The functions of the fuel pump strainer are to filter contaminants and to wick fuel.

The life of the fuel pump strainer is generally considered to be that of the fuel pump. The fuel pump strainer is self-cleaning and normally requires no maintenance. Fuel stoppage at this point indicates that the fuel tank contains an abnormal amount of sediment or water, in which case the tank should be thoroughly cleaned (See "Fuel System Cleaning"). If the fuel pump strainer is plugged, replace it with a new one.