Fuel gauge stuck on full

[thecantaloupeman]

So I just fixed my fuel tank leak and replaced the filler hose. Just when I thought I fixed it and left to get gas, I noticed the gauge was stuck on full. No more leak, but now I can't tell how much gas I have. It had a half a tank before the gauge stopped working. I am not sure if this had something to do with me taking the hoses off, and starting the truck without them on, or if it is just a total coincidence and something electrical failed. How can I go about diagnosing this?

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[73c20jim]

Wow. Same exact post as mine posted a couple of days ago. Search is your friend.

 

[thecantaloupeman]

Wow. Same exact post as mine posted a couple of days ago. Search is your friend.

Well I'm on Tapatalk so that's prolly why I didn't see it, but we'll figure it out together! I'll go see if I can find your post.

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[bedwards]

A loose or disconnected wire or ground will cause a over full tank on the gauge.

 

[thecantaloupeman]

A loose or disconnected wire or ground will cause a over full tank on the gauge.

That could make sense because I bumped the tank a few times with the screwdriver when I was getting the hoses off. How can I find my ground wire though?

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[73c20jim]

I had a bad contact between the gauge and the panel. Now it shows empty all the time.

Having problems with other gauges also.

Quick fix. I gave up and bought an electronic panel and should arrive soon.

Have two sets of 1973 gauges and one set of 198? gauges I have no use for.

 

[73c20jim]

https://www.gmsquarebody.com/threads/gas-gauge-goes-to-full.26243/

 

[DirtyDYT]

A loose or disconnected wire or ground will cause a over full tank on the gauge.

My K30’s gauge would only read correct with the send wire connected and the ground disconnected. If you connected the ground it showed over full until it dropped to about 3/4 by the time it was empty. This was true with the old original(?) tank and the new tank and sender. Maybe the senders had different ohm values over time?

 

[thecantaloupeman]

https://www.gmsquarebody.com/threads/gas-gauge-goes-to-full.26243/

I read through your thread, but your problem must be different than mine. My gauge goes way past full. And it doesn't move when I start it. Even with the key off, the gauge is all the way past full. How do I check my ground wire? I know nothing about how it's layed out

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[Charlie]

I read through your thread, but your problem must be different than mine. My gauge goes way past full. And it doesn't move when I start it. Even with the key off, the gauge is all the way past full. How do I check my ground wire? I know nothing about how it's layed out

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Mine was showing at 3'oclock position always. Replaced sending unit, fixed. There is a ground wire near tank mounted on the frame. If it worked before hose change, you mentioned you bumped it with screwdriver, then it may have knocked wire off of sending unit. Hard to tell if it did, but you can take a look to see. May be able to see between cab and bed but it is still hard to see.

 

[bedwards]

There is a ground that goes to the sending unit on each tank. Mine did the same thing, well past full, and I laid on my back and reached up on top of the tank and worked the connectors enough to get them where they made contact again. That's been a couple years ago and they have worked ever since. There are connectors as well in the valve if you have dual tanks. A lot of electrical gremlins in cars can be traced back to bad/corroded grounds.

 

[Rusty Nail]

I filled my gas tank today..

 

[FireAndDarts]

Have you checked your fuses? I know it seems obvious, but didn't see that mentioned.

Someone, on another site suggests "A fuel gauge that looses battery voltage will stay in its last position it had with power until the problem is repaired."
So it may make sense that gauge is stuck in one particular position. (Check for unplugged wires!)

We just got a 1980 C10 and I've been going through assorted electrical issues - grab a copy of the wiring diagrams that match your truck from the reference sticky thread.

Then, you are tracing back from the gauge to whatever it connects to until you find the issue. Color-coded wires help
There are easy ways to test as you go - but having the right diagrams is very helpful.

 

[73c20jim]

I filled my gas tank today..

How much did it cost???

 

[Rusty Nail]

Damn near sixty bucks!