Fuel gauge started reading past full mark all the time (1 Viewer)

[Hamachi]

My original fuel gauge was working fine, then it started reading past the full mark all the time and won’t budge when fuel is lower. I pulled the float out and tested it - the fuel gauge goes down when I lower the float and up when I raise the float. Does anyone here have any idea what the problem could be?
I have a 1977 fuel gauge and tank set-up
thank you

 

[tornadoalleycruiser]

Ground fault in the wire to the gauge or bad sender. Rubber gasket on sender ? Test continuity from the sender wire to chassis. If you have continuity then prob a spot in the wire touching ground. When you removed the sender and tested it worked? When you removed it you used a jumper to the tank for ground? if all the above is true I would start with a new gasket. Test and report back. Cruiser outfitters sells the gasket. Apprx $5 or so.

 

[Hamachi]

Ground fault in the wire to the gauge or bad sender. Rubber gasket on sender ? Test continuity from the sender wire to chassis. If you have continuity then prob a spot in the wire touching ground. When you removed the sender and tested it worked? When you removed it you used a jumper to the tank for ground? if all the above is true I would start with a new gasket. Test and report back. Cruiser outfitters sells the gasket. Apprx $5 or so.

Thanks for the info. The rubber gasket is new as well as the sender and wiring.

Yes, I had the sender grounded when I tested it out of the tank.
I will test continuity today.