It's a fairly simple circuit,
Power from key to the gauge ( battery voltage )
ground wire from gauge to the sending unit center stud ( wire harness )
Sending unit has variable resistor ( changes with fuel level )
Resistor to sending unit frame ( must be out of tank to verify )
Sending unit mounting screw to frame rail of truck wire ( must have clean metal to metal contact at tank and frame rail)
and now you can ad internal ground inside gauge as shown above.
Work your way back and you will find the problem.
Last edited by Joe H; 01/07/2021 2:23 PM.
