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/TechSpkgFUELSENDINGUNITS06-2005.pdf
FUEL SENDING UNITS What is a fuel sending unit A device located in the fuel tank that measures the fuel level What does it consist of A float usually made of a coated foam substance A swing arm for the float A variable resistor A series of feed return and vent tubes welded into a round housing Electrical harness for the variable resistor Electrical harness for the fuel pump negative and positive feeds A fuel strainer Tank sending unit lock ring and O ring seal Fuel pump coupler hose and clamps How does it work The variable resistor uses a rheostat to vary the amount of ground signal The ground signal reading determines the fuel reading on the gauge The resistor is directly connected to the float arm The fuel level determines the position of the resistor Why do they fail Rust damages the feed vent tubes Fuel vent lines damaged when fuel pump is serviced Floats lose the protective coating causes float to sink Feed vent tubes damaged or broken off when servicing fuel filter or rubber fuel lines Rheostat becomes defective wire breaks or wears out Float damaged when servicing the fuel pump Float is damaged when trying to twist the arm out of the sending unit hole in tank Why replace the entire unit It s cost and time efficient Higher profits Ease of installation Prevents comebacks Unit may fail shortly after tank fuel pump service Fuel lines and fittings are damaged during service too long to repair Floats often go bad or are damaged Complete product includes strainer etc
