Installed new gauges with new dash & wire looms a couple years ago. Everything works except fuel gauge. Decided to get fuel gauge working. Tested black wire at sending unit for ground that was screwed in to bottom of trunk floor pan. The pan is not grounded. I then looked for a ground on the rear frame. No ground found. I did grind off paint before testing. I did manually supply ground to the black wire to the sending unit and gas gauge did move just under a full tank which I believe is correct. In the engine bay I have ground on fire wall, engine, fenders, radiator support, and frame. Do I need to run under the car a ground wire off the battery back to rear to obtain a ground?
No ground for fuel sending unit
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No, a short piece of wire from the negative battery cable to the fender grounds the body,
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Check this and if it still doesn't work ground the frame to the body at the rear of the car or where your sender gets ground. Your body should actually be grounded at the right fender near the battery and the frame grounded to the body near the right footwell in the lower right engine bay.
I've actually seen this happen on a restored car. Everything gets painted/ new rubber and bushings and the panels don't transfer ground.
Everything suggested in engine bay is grounded. Negative battery cable wire to right fender. I then went from that ground to also ground right frame rail. Heavy Battery negative wire grounded to engine. Firewall grounded to each head. Again, in engine bay both fenders are grounded as well as both frame rails, engine, fire wall, radiator support. In rear of car I take a rotary disc grinder to both frames and to trunk pan before testing. No ground. In a few days I can borrow a lift from a friend so I can check things out better under the car. I’m getting too old & out of shape to be crawling under a car on jack stands. Thanks to all for your suggestions.
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If your frame is grounded at the front of the car then the entire frame is grounded. If your taillights and signals work correctly, the rear sheet metal of the car is grounded. The only way I can see no ground to the trunk pan is if it was replaced and seam sealer used to mount it.
I am an idiot. My testing procedure for finding ground on Chevelle was faulty. I have a tool that when connected to battery the probe on tool will indicate if it is a ground or 12 volt. It also will send a positive 12 volt or ground. But what I couldn’t find for the tool was the extra cord which allows to extend the range by 10 feet. Therefore I attached tool to battery in car when testing under hood which always worked great. But when attached tool to a spare charged battery from shop that I placed on floor when workin at rear of car, never could find ground there. After 8 hrs trying this & that and seeking help from you And coming to the conclusion I had to run a ground wire to the rear, I by accident discovered that my tool only works properly when tool is connected to the battery INSTALLED IN THE CAR. After grinding area underneath floor pan to metal & attaching ground wire to sending unit. Gauge is working. Again, I thank all you for your help. Each one of you were spot on in ways to solve my problem. This person on the receiving end of the advice was just slow in his problem solving skills.
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