Bad Fuel Gauge?

[1986B24x4]

I recently replace my fuel pump and sending unit in the tank because my fuel gauge was jumping around and read different all the time. After I replaced it, it stays full for a while then drops to half a tank. Doesn't read anywhere inbetween. Is there something else I could replace? The gauge in the dash possibly? Does that go bad? I'm at a loss here.

 

[PetesPonies]

The gauge works by the sending unit in the tank varying the resistance as the float moves. The gauge in the dash shows thew results based on that resistance. If the wire is totally grounded ( practically zero resistance ) the gauges pegs to the right. OK, for you I would guess the gauge is working fine. It just reflects the resistance given it. Unfortunately my experience with "new" sending units is most of them are crap.

 

[1986B24x4]

Well hell. And my luck, I just filled up today. Guess ill wait til next week to pull the tank, AGAIN.

 

[PetesPonies]

You could pull the wire at the tank and connect it to a rheostat and ground one side of the stat. That way you can turn the knob and adjust the resistance, to see if the gauge functions as it should.
Also, don't many here cut access panels to get to the tank easily without pulling it?

 

[1986B24x4]

I'm sure they do cut holes but mine is a mint, all original '86. Ill drop the tank. I'm not that lazy.

 

[PetesPonies]

Then setup the variable resistor and find out for sure before you drop it again.