fuel tank ground - Vintage Mustang Forums

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post #1 of 6 (permalink) Old 12-21-2010, 03:15 PM Thread Starter
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fuel tank ground

Having trouble with gas gauge not reading. It's a stainless 22 gallon, with a scott drake fuel sending unit. Car should have gas in it, that or it's getting 3 mile to the gallon. Gas gauge doesn't work, grounded the wire and the gauge moves accordingly. Only thing I can think of besides a faulty gauge is that I used body puddy (dum-dum) in the black caulk strips to seal up the tank to the flange it sits on. Then used the screws to bolt it down. Do I really need something more then that, or does the 10+ screws suffice for a good body to tank ground? Car runs out of gas, real quick, it'd be nice to have the tank actually read. The float is brass, didn't have any fluid in it when I pulled it the other day
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post #2 of 6 (permalink) Old 12-21-2010, 03:27 PM
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How is wire between gage and tank sending unit ? Might try disconecting at both ends and then connecting ohm meter between one end and body ground. You should get no reading (open circuit). If you get zero or some reading of resistance I would suspect a bad wire. Another way to check would be to run a temporary wire between sending unit and gage. If gage the reads you know wire is bad.

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post #3 of 6 (permalink) Old 12-21-2010, 05:30 PM Thread Starter
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Gauge reads when I ground it. Thats the best part. Just really considering that my tank may not be fully grounded, but I do have all the screws in place and a new tank etc.
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post #4 of 6 (permalink) Old 12-21-2010, 07:58 PM
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Hi 70Mach,
I just changed the tank on my 66. Seems the previous owner had chaulked in a replacement tank at one time. I did not scrape off the chaulk, my new sending unit did not "send" either. I backed out one of the bolts holding in the tank, put a wire under it, and screwed the other end into the body behind the rear seat. Fuel gauge works Perfect now. May be worth a try. Good luck.

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post #5 of 6 (permalink) Old 12-21-2010, 08:29 PM
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Sounds like you may already know the problem...A bad ground. Having a fuel tank with a weak ground sounds like bad news anyway. I agree with all the screws in there it should be grounded but I'd back 'em all out and make sure each one is hitting bare metal in the trunk and on the tank. You may have done a spectacular job with rustproofing your truck!...which is not a bad thing for Charleston.

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post #6 of 6 (permalink) Old 12-21-2010, 08:35 PM
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The 10 screws should be plenty, unless you insulated them. Try grounding the gauge wire that connects to the sender, to the tank itself. If you get strong movement, the problem is in the sender. It's possible that the float is stuck or the sender is defective. If it doesn't move, but will grounded elsewhere, the tank needs to be grounded.

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