Fuel Gauge stuck on 3/4 - need advice where to start... - JeepForum.com
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post #1 of 5 Old 05-27-2020, 11:43 AM Thread Starter
ccoyle71
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Fuel Gauge stuck on 3/4 - need advice where to start...

Thanks in advance - I love this forum, and although time and money (and stage of life) have limited my ability to tackle Jeep projects, I still read the forum - almost daily. Everyone has been most helpful over the years!



I have an 86 CJ7 - and ALL the gauges worked, until recently. My fuel gauge doesn't go below 3/4 of a tank. If I fill it up completely.....it will go up and peg all the way at the "F".....and as I drive it....gradually drop to 3/4 but will never go below that.


Can someone give me some advice on where to start? Is there a float in the tank? I have the FSM - but I'm having trouble finding where there is a blowout of the parts associated with the fuel tank / gauge....unless I'm missing some of the manual. The only fuel related systems all deal with under the hood - not with the tank - at least on my version.


Thanks a ton!!!

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post #2 of 5 Old 05-27-2020, 11:47 AM
John Strenk
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Yes there is a float in the tank.
The wiper could of gotten stuck on the windings in the sending unit but unlikely.

But I would check to see if regulator is working on the fuel gauge.
Terminal "A" should flash it you put a test light on it. Ground the test light to the battery (-) post. Don't ground it to your dash, that may be the problem.

It could be a simple ground problem.


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post #3 of 5 Old 05-28-2020, 08:30 AM Thread Starter
ccoyle71
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Quote:
Originally Posted by John Strenk View Post
Yes there is a float in the tank.
The wiper could of gotten stuck on the windings in the sending unit but unlikely.
But I would check to see if regulator is working on the fuel gauge.
Terminal "A" should flash it you put a test light on it. Ground the test light to the battery (-) post. Don't ground it to your dash, that may be the problem.
It could be a simple ground problem.

Thanks John. I did find some instructions in the FSM under the instrumentation section - a diagnostic tree / charts. I'm still not able to find any diagram of the tank, float, etc....
As you suggest, I'm hoping it's something simple and not inside the tank - but I'm slightly concerned as it does "work" when it's between the range of 3/4 full to full. The diagnostic tree in the manual doesn't even really reference that problem, which makes me think it may be the float.

I'll test tonight as you suggest and report back. Thx for your help!
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post #4 of 5 Old 05-28-2020, 11:26 AM
jeepdaddy2000
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You might also try disconnecting the wire from the sending unit. If the gauge drops to E, then the issue is probably in the tank. If it drops back down to 3/4, then the gauge may be stuck.

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post #5 of 5 Old 05-28-2020, 12:22 PM
oldschool74cj5
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hello

over the years of many jeeps fuel gauges i use the only reliable one i have. the speedometer. i fill up every 150-200 miles. for me that is 1/3 to 1/8 of a tank. when i was young and had a 401 in a 7 i carried a jerry can. when she sputtered it was time to dump it in and go fill both of them up.

oldschool
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