gauge sitting at about 3 oclock, checked and cleaned ground wire at tank where it attaches to body, what next?

GM gauge works by tank unit controlling resistance to ground 0 to 100 ohms. You need to access the wire to the tank unit. With the key on you should have power on it and if you ground it gauge should go to empty.

Shouldn't the gauge go to full if you ground it?

Should go to empty if you ground the wire from the gauge, goes past full if open.

quote:

Originally posted by Eman:
Should go to empty if you ground the wire from the gauge, goes past full if open.

so it should have 12 volts in trunk tan wire key on?

If that's the wire that comes from the gauge to the tank unit. I can't remember if it will have 12v or if it's less. It should light a test light.

hell fuel gauges go to full? Wish you could teach my truck that trick.

Standard test light at the tank should get you about 1/2 full reading.....all GM's were on a 90ohm gauge scale.
Doesn't work that way on Phords and Chryslers. They will have a 12v pulse from the CVR in the gauge panel, grounded wire at the tank will get a full reading.