Fuel gauge - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

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post #1 of 4 (permalink) Old 05-27-2018, 01:04 AM Thread Starter
Join Date: Jul 2017
Posts: 24
Fuel gauge

While working on my brakes, I noticed a wire coming off my gas tank. I think it is the wire that goes from the fuel sending unit to the fuel gauge, which doesn't work (if I am right, could be a darn good reason why it doesn't work).

Would appreciate any thoughts on this. If it is the wire from the fuel sending unit, is it simply run to the gauge where I could just connect it?

Thanks, Mike
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post #2 of 4 (permalink) Old 05-27-2018, 08:07 AM
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Location: Coopersville, MI
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Not sure if it is the ground wire or the wire that goes to the gauge, but it definitely looks like the cause of a fuel gauge not working. If it is the ground than you just need to figure out where the ring lug is for it. If it is the hot wire then you need to find the other end. Could put a jumper on it and tie it to the chassis as a test. If the fuel gauge goes to approximately the right tank amount it's the ground. If it pegs out as full then it is the sensing wire.
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post #3 of 4 (permalink) Old 05-27-2018, 12:12 PM Thread Starter
Join Date: Jul 2017
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It is the only wire coming off the sending unit (that I can see anyway). The way it is tied around the line rather than just grounded is what made me think it was the gauge wire (I have found many wires just taped to things, tied to things or simply hanging since I bought the car and have been trying to bring it back to life - best example was a wire running along the intake and just taped to the hose running from the carb to the valve covers, still have to figure out what this is, its heavier gauge, maybe the AC power wire).

Since posting this, I have read that the power/gauge wire drops down from the rear harness and this should be the ground wire, this is based on info from a full size Pontiac, but I assume that most full size GM cars are similar. If this is wrong, I would appreciate any info. I am going to try it as was recommended by Deadwolf. Hopefully one more thing to cross off the list of things that need to be done - which seems to actually increase as I dig in rather than grow shorter.

Its amazing what I have found as I am trying to get the car able to run as I just lost my garage space and have to find another. Good times.

Last edited by miterry; 05-27-2018 at 02:11 PM. Reason: updated information.
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post #4 of 4 (permalink) Old 05-27-2018, 03:02 PM
Join Date: Jan 2006
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Wire comes off of the INST fuse box hot, then runs up through the gauge (it measure the voltage in the wire) before it drops down to run to the trunk, where it grounds out by way of going through the 90 OHM rheostat that is the sending unit. The tank has to be grounded (a separate wire from the sending unit to the frame) to work. A simple DC circuit that can be easily tested with a voltmeter.

Big Dave
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