Fuel gauge wiring problem

[ejrossi]

I have a 71 F100 with a Cleveland 351 that the previous owner installed. They also installed aftermarket gauges for temp and fuel. The temp is right but the fuel doesn't read correctly. the temp had to use different wiring and the gauge wiring for temp is not connected to anything. Does this "loop have to be closed for the original fuel gauge to work? I can get the original fuel gauge to move when I ground the wire going to it and seem to have the wires connected correctly from t
He tank to the gauge. When looking at wiring diagrams I can't tell if the two gauges and wiring have to be in a closed loop for the original gauge to work. Need help!

[71PA_Highboy]

the fuel gauge takes power from the Instrument Voltage Regulator (IVR) on one side. and a direct wire to the fuel sender, which is a variable resistor, then to ground.

on the original gauge the IVR puts out ~6v pulsed dc.

to test the gauge, hook up the IVR and short the sender wire to ground. this should peg the gauge.

to test the sending unit, remove from the take, hook up an Ohm meter to the wiring stud and the flange, then move the float thru its range... IIRC it will be 0-75 ohms.

good luck.