fuel guage

[bean]

I know this has been answered before but how do you test to see if the guage is bad or if the sending unit is bad? Would like to be able to drive my truck farther than I am now. Thanks.

[JimKshortstep4x4]

A quick test is to disconnect the brown sending unit wire from the tank.

With the key on and the wire disconnected the gauge should go past full. With the key on and the wire grounded the gauge should read empty. This is not a fail safe test but if the dash gauge works as described then chances are the tank unit is bad. You can further test the tank unit with an ohm meter and it should read between 0 and 90 ohms. (If you don't get any results then there is a possibility that the wire is bad or the dash gauge is bad).

(Tha dash gauge is calibrated to indicate empty with a 0 ohm signal and full with a 90 ohm signal from the tank unit).


Jim

[Longhorn Man]

If your guage is always showing empty, then, after doing as Jim said, pull the chrome thresh hold in the door jamb. Odds are, the wire is grounding out under there.
And if it is way past full...there's a strong chance that the wire is sevored under there, so pulling it would still be a good idea.

[jtminton]

What happens if your gauge is always showing half tank like mine? (I haven't tried the trick above yet, but will when i get home)

[Longhorn Man]

The it is more likley to be a lack of power through the circuit board, or a bum guage.

[muddpile]

I have a non-working fuel gauge too (or sending unit) and was wondering how I'd test. My gauge reads WAY past full (the needle is horizontal on the full side. So that means my brown wire might be cut or unhooked right? I'll have to go test this tomorrow. Right now I just use a piece of hose and dip it in the tank every once in a while to see how much gas I have.