fuel tank sending

Make sure there is a good ground to the sending unit. Factory uses a metal strap which clipped to the male fuel fitting on sending unit bridging the rubber coupler and the other end clipped to fuel line.

Sometimes that strap becomes lose, rusts apart, or fuel line loses its ability to provide a competent grounding point. This lack of ground at sending unit is the cause of gage not working more often than not.

You can order a new strap, or make up a jumper wire using a few small hose clamps to attach to steel lines accomplishing the task of grounding sending unit.

Another test you can do is to check the resistance of the sending unit. It should be anywhere between 10 and 75 ohms give or take depending on level of fuel in tank. Just touch one VOM probe onto electrical stud at sending unit, and the other to its fuel tube.