Today i fixed my fuel level gauge issues on my 2001 Grand Prix se 3.1 after a year of headaches and i felt i should share my findings because i never found a final fix on any forums and hopefully i can help save somebody alot of time and money.
my issue was that when i first started my car, my fuel gauge would swing to full and after about 10 seconds it would plummet down to empty as long as it was in neutral. in gear the gauge would drop much slower but it still would never indicate the proper fuel level. very frustrating.
first i will say that the final fix was to add a new chassis ground to the vehicle with just a short section of 4 gauge power wire i got from my old speaker system. it might be overkill but it was cheap.
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now this in the end fixed my specific issue but here is some information for those who this does not resolve the problem.
first, you will need a multimeter that has a resistance setting as well as voltage.
the first step i would recommend before anything is to check the quality of the body ground. all i did to check this was to connect my multimeter to the positive side of the battery and the negative (should read 12+ volts with the car off) just to make sure the multimeter is operating correctly and that i have it on the proper setting. next i took the negative probe of the multimeter and stuck it to the bolt that ties the chassis ground cable to the body. it should again read 12 or more volts. in my situation it read 5 volts. obviously an issue. so instead of removing the factory chassis cable i just disconnected the bolt to the negative terminal of the battery and connected the ring terminal on the end of a section of 4 gauge wire and screwed it back down. the other end i attached to the inner wheel well after grinding the paint away and applying dielectric grease to ensure it keeps a good ground for a while.
now if this doesnt fix your issue well then we can move on to the next step.
