77 chevy shortbed 350 fuel guage

[4X4rock]

My 77 chevy 350 AT shortbed's fuel guage is on full when key is off. It goes way past full when key is on. This truck has dual fuel tanks. I don't have clue as to how the dual fuel tank system works. Any suggestions are greatly appreciated.
thanks

I found some very helpful solutions n previous posts!
thanks

[Mebes]

I just fixed a fuel gage in a 79 chevy about a month ago for a buddy.
It was a short box with only one tank but i'm guessing that it has a similar setup.

The fuel gage sender wire travels along the frame on the passenger side frame rail, and goes past the wires to the starter.

Up into a tube that is placed there to protect the wires from the heat of exhaust system.

Someone had replaced the starter and not reattached the tube.

The fuel sender wire melted against the exhaust and severed.

I fixed it up with a 6 inch piece of wire and a couple of shrink type butt connectors.

Good luck.
Mebes