Fuel gauge stuck past full

blackbuck350

Apprentice
Thread starter
May 2, 2019
71
8
I just checked the ground wire coming straight from sending unit and grounded it straight to the negative side on my battery still no change, so is it another way or some other place to check for bad ground?
 

84 W40

G-Body Guru
Dec 9, 2009
514
93
This is a picture of a friend's sending unit that I replaced on his 86 442 about 6 or 7 years ago and it was original. He had the same problem your having but I found two problems with it, 1. The float would stick in the full and half full position 2. the braided ground wire that attaches to the sending unit with push pin see picture with circle had rust and corrosion on it giving a bad reading over full. We replaced it with a new unit.
20210709_210952.jpg
 
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blackbuck350

Apprentice
Thread starter
May 2, 2019
71
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The sending unit has been changed once already with a aftermarket I just can’t remember which one I replaced it with
 
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g0thiac

G-Body Guru
Sep 6, 2020
753
63
The sending unit has been changed once already with a aftermarket I just can’t remember which one I replaced it with
Make sure none of the wires are broken going into it.

And an easy way to check a ground is to just bolt it somewhere else, or if you really want to be sure, run a long wire to the negative side of the battery.

But I do think it is the white wire coming out of the tank to the dash. I wouldn’t do a continuity test, only because even if its damaged, even if there was only one strand that still conducted current, it could be quite deceptive so heres two possible options.

You can use ohms and test it that way, see if it goes to zero when you move the white wire around coming from the tank.

Or, you take out your gauge cluster, then go to the tank, cut and wire an extension from the white wire and touch it to the back of the terminal on the fuel gauge, and see if it moves.
 

blackbuck350

Apprentice
Thread starter
May 2, 2019
71
8
Make sure none of the wires are broken going into it.

And an easy way to check a ground is to just bolt it somewhere else, or if you really want to be sure, run a long wire to the negative side of the battery.

But I do think it is the white wire coming out of the tank to the dash. I wouldn’t do a continuity test, only because even if its damaged, even if there was only one strand that still conducted current, it could be quite deceptive so heres two possible options.

You can use ohms and test it that way, see if it goes to zero when you move the white wire around coming from the tank.

Or, you take out your gauge cluster, then go to the tank, cut and wire an extension from the white wire and touch it to the back of the terminal on the fuel gauge, and see if it moves.
Yes already grounded it to negative battery doesn’t make any difference, just gonna replace sending unit just having hell finding one hopefully the one I pull out will have a part number
 
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69hurstolds

Geezer
Supporting Member
Jan 2, 2006
6,814
113
How about pulling it out of the tank, first, before just going and buying another sending unit. Then, plug the wiring in, ground the ground wire, and move the float by hand with ignition on. If the gauge moves, it's the wiring and/or connections. Check the wire push pin UNDER the sender cover plate to make sure it's tight. Make sure no connections are open. If it still doesn't work, then it's probably fubar. If you just replaced it recently, why is it dying so fast?

Assuming you're talking about a wagon tank, 25000757 is your sender's GM part number best I can guess. Has 2 lines. Not sure about the aftermarket equivalent. If yours has 3 lines, not sure about that one.

There's rumor the carbureted Astro van sender works as it's the same length, but I don't know. Maybe the wagon heads can chime in here. My knowledge as a Wagonista is insufficient.
 

69hurstolds

Geezer
Supporting Member
Jan 2, 2006
6,814
113
Here's a real basic GM fuel sender. Nothing to them, really. So if your sender isn't working, and can't find a perfect replacement, you MAY be able to "refurbish" yours by popping off the cap and doing a little cleanup on aisle 5. Note in the video below, about part way through, he loses the spring on the end of the float pivot and never addresses it. You need to keep that spring on there.

 

blackbuck350

Apprentice
Thread starter
May 2, 2019
71
8
It was replaced
How about pulling it out of the tank, first, before just going and buying another sending unit. Then, plug the wiring in, ground the ground wire, and move the float by hand with ignition on. If the gauge moves, it's the wiring and/or connections. Check the wire push pin UNDER the sender cover plate to make sure it's tight. Make sure no connections are open. If it still doesn't work, then it's probably fubar. If you just replaced it recently, why is it dying so fast?

Assuming you're talking about a wagon tank, 25000757 is your sender's GM part number best I can guess. Has 2 lines. Not sure about the aftermarket equivalent. If yours has 3 lines, not sure about that one.

There's rumor the carbureted Astro van sender works as it's the same length, but I don't know. Maybe the wagon heads can chime in here. My knowledge as a Wagonista is insufficient.
about 2yrs ago when I replaced the new tank, it had been working fine filled up and im it went way past full and didn’t come back up to full
 
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g0thiac

G-Body Guru
Sep 6, 2020
753
63
Yes already grounded it to negative battery doesn’t make any difference, just gonna replace sending unit just having hell finding one hopefully the one I pull out will have a part number
For sure, the Spectra Premium unit I got through the dealer was easy to find 2 years ago. Now it's difficult and I don't blame ya.

Anyway, like 69hurst said you can repair it yourself. But if it was a new unit, I really do think it's the wire that runs to the gauge cluster.
 

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