Goofy Gas Gauge '82 C-10
 

I'm no electrical wiz so I'm easily stumped. So I'm looking for advice.

PROBLEM: 1982 C-10 that the prior owner just cut every corner possible on any repairs he did. 1st Gas gauge read half to empty only. Tank had a leak so when I replaced that I replaced the sending unit. Gauge still read the same. Obtained a used Gauge from a member here that I was told was in good working condition. Installed that one. It now reads over full by 1/4 tank at least and doesn't appear to be dropping with truck use.

A couple of variables that may be playing into this:
I believe the truck was originally a 6 cyl. It now has a "newer" V-8 with an A/Market electric fuel pump and the motor has an electronic ignition with a carburetor. The wiring to the gauge appears to be fine.

I know tough to diagnose on-line but I thought I'd throw it out there.
Thanks Bacca

Re: Goofy Gas Gauge '82 C-10
 

The gauge at 3'oclock is a missing ground or broken/corroded wire.

Single tank? The dual tank switches can go bad and cause this.

Pretty much all of the GM gas gauges from this time period use the same resistance curve in the sender.

Re: Goofy Gas Gauge '82 C-10
 

Thanks Dead Parrot

I should've added that it's a single tank. In regards to bad ground. Would that make both gauges do different things?

Thanks Bacca

Re: Goofy Gas Gauge '82 C-10
 

Your first sending unit may have had a pinhole in the float which would have made it heavier than a full tank of gas could have lifted it. The second gauge would have red the same with that sending unit. A bad ground or sending unit wire will cause the second tank sender to give the over full reading, as was said.

Run a temporary wire from the sending unit flange to a good ground and run a new wire from the sending unit terminal to the gauge.
Alternatively you can pull the sending unit and ground the flange with the terminal wire attached and move the float up and down with the key on and watch the gauge for movement E to F.

The 67 to 72 models run the sending unit wire to the fuse panel to the FUEL terminal and from there the wire goes to the fuel gauge in the dash. I am not sure how the 82 is setup.

If you ground the sending unit terminal on the fuel gauge it will read to empty.
This should tell you if the gauge is OK.

Since you got the same readings with 2 gauges on the first sender, I doubt that the resistor on the gauge is bad. That will usually cause the gauge to read up to 1/4th tank and no more.

Re: Goofy Gas Gauge '82 C-10
 

Thanks VetteVet,

This is a great starting point for me.

Bacca