fuel gauge problem

[eddyw]

What could be the problem?

The little fuel gauge in the dash cluster always indicates full tank(tank is not full).

This is the second fuel sender in the fuel tank and still have this problem from beginning.

 

[TheRktmn]

Does it read full when you disconnect the wire from the sender?

If so, you have a short to ground on the wire from the gauge to the sender or your sender is going to ground.

If it goes to Empty with the wire off you probably have a bad IVR.

http://www.classiccougargarage.net/showthread.php?tid=186

 

[Don C]

Disconnect the wire from the fuel sending unit, see if it goes to empty, if so it's the sending unit providing a continuous ground, if not, you have a ground (short) between the gauge and the sending unit. Due to problems with old circuit boards I would start troubleshooting on the dash end, looking for shorted traces on the circuit board and check the voltage output of the instrument voltage regulator. Then work your way back with an ohm meter, checking after each connection to see if you've found the location of the ground.