1991 Mustang LX Fuel gauge shows full

Blueinfan said:

Hi All,

Just installed a new fuel tank with a new pump, and wires. I turned on the car and the fuel gauge shows full. Can't be full because I only poured 5 gallons of fuel. The car has the original instrument cluster and all the other gauges work but the fuel gauge.

thx

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Mustang5L5 said:

Can you still access the plug to the fuel pump from the back? 2 wires are for the pump, and 2 are for the sender. I can get wire colors later.

Measure the resistance of the two sender wires. Empty is 22 ohms. full is 145 Ohms. With 5 gallons in the tank, i would expect to see something like 30-50 ohms. Grounding this wire out will peg the fuel gauge to max

With the harness unplugged. Cycle the key and see where the fuel guage moves to. Unsure if it will actually move with it unplugged so don't read into it too much if it does nothing.

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