Gas Gauge question

[Kain]

So the gauge quit and when I unplug the sending unit the gauge does nothing. I believe that is the gauge itself. Am I wrong?I
will clean the ground today and check anything I can without pulling the cluster.

I have a new gauge, if need be I will install it. I just want to double check before yanking cluster out.

 

[Bent77]

So the GM gauge in sending unit work on the ground side, so if the sending unit doesn’t have proper ground, the gauge won’t do anything

Typically, if the gauge is working, and you unplug the sending unit, then the gauge will spike one way or the other

 

[Blue85]

You can also put the cluster flex circuit in question, as they do flake out sometimes. If you're digging into it, you should be able to measure the sending unit resistance from the gauge pins or the cluster connector. It's 0-90 Ohms, but should be infinite with the sender unplugged. Also, if you're unplugging the sending unit, that connector is a good place to probe. Divide and conquer and all that.

 

[Barrman]

If nothing changes when you unplug at the tank, try grounding that wire. The sender changes resistance between 0-90 Ohms. 0 Ohms is empty. So, if you ground the wire the gauge should go to empty.

I love the military Technical Manuals but really get aggravated when it say “trace circuit.” Which is exactly what it says for the CUCV fuel gauge after you check the actual gauge for having 12 volt positive and negative to turn on and nothing happens when you unplug at the sender. My first M1009 (1984 K5 wiring) had the same issue as yours sounds like. It turned out to be a broken pink wire above the rear axle. It wasn’t broken it 2 either. The insulation was still good but running my fingers along the entire wire end to end let me feel the broken wires inside.

 

[Kain]

well that worked , cleaned grounds and then grounded that pin and the gauge come back to life.

 

[Barrman]

Great!