Fuel Tank Unit: Description and Operation

Description:

DESCRIPTION
The fuel sender assembly is attached to the top of the fuel tank, and extends from the top of the fuel tank to the reservoir.

The fuel sender assembly consists of the following major components: a fuel sender, a fuel pump, a fuel pump strainer, a fuel level sensor assembly, a fuel pulse dampener, and a roll-over valve.

FUEL LEVEL SENSOR
The fuel sender is a ceramic card assembly that consists of the float, the wire float arm, the rheostat and the roll-over valve. The fuel level is sensed by the position of the float and float arm, which operates the rheostat.

The rheostat is mounted on the fuel sender and located in series with the voltage supply circuit from the fuel gauge. As the position of the float varies with fuel level, the rheostat produces a variable resistance between the fuel gauge. The fuel gauge converts this variable resistance into the fuel level reading display on the instrument panel.

An isolated circuit is used in this application. The isolated ground circuit uses a dedicated ground wire from the rheostat to the fuel sender connector. The isolated ground circuit is used to prevent erratic fuel level readings caused by a difference in voltage potential among vehicle ground points. An isolated ground terminal is connected electrically to one end of the ceramic card.

FUEL SENDER STRAINER
The function of the fuel sender strainer is filter contaminants and to wick fuel.

ROLL-OVER VALVE
The roll-over valve is pressed into the [1][2]EVAP pipe 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 EVAP pipe to the evaporative emission canister.