patrickm -
Is your gas gauge a 12v reproduction? I installed a 12v gauge from The Truck Shop on my '54 a couple of months ago and like yours, it does not return to EMPTY with the ignition off. Since the gauge is located at 2:00 on the gauge cluster, gravity sometimes pulls the needle past full with the ign off as you describe. Otherwise, it works fine. (FYI - The 12v gauge is manufactured differently than the original 6v gauge. Three coils instead of two).
This Fifth Avenute Tech Tip seems to describe your problem:
6) If dash gauge reads, FULL when tank is known to be only half full the wiring between the tank or the sender is bad. Ground the gas tank sender terminal using a jumper wire, if the dash gauge still shows full there is bad wiring between the dash gauge and the tank sender. If the dash gauge goes to empty, the gas tank sender is defective.This is the link to the full article.I made sure that everything is grounded well.
- bare metal on the inside of the gauge cluster where it contacts the back of the gas gauge
- bare metal on the outside of the cluster where it contacts the mounting nuts,
- jumper wire from a good ground to one of the screws that attach the sending unit to the tank.
FWIW - I tested my gauge before I installed it, however, it only read EMPTY after I installed it. I found that I had over-tightend the terminal on the sending unit that held the rheostat unit to the round body of the unit. I had collapsed the insulation or maybe rotated the rheostat unit to allow it to touch the body.
Good luck,
