fuel gauge wacky on front tank only

tomtoc · Jul 3, 2008

driving down the highway, I downshifted to get up a hill, and noticed my fuel gauge went all crazy. It was at 3/4 of a tank and shot up way past full. It keeps jumping between full and way past full every few seconds.

It just randomly happened. Rear tank is fine. Likely culprit? Should I still run it like that on the front? Runs fine, just don't want to hurt anything electrical.

blacksnapon · Jul 3, 2008

tomtoc said:
driving down the highway, I downshifted to get up a hill, and noticed my fuel gauge went all crazy. It was at 3/4 of a tank and shot up way past full. It keeps jumping between full and way past full every few seconds.

It just randomly happened. Rear tank is fine. Likely culprit? Should I still run it like that on the front? Runs fine, just don't want to hurt anything electrical.

It kind of sounds like you're intermittently losing ground. An easy test to see if you're losing ground, is to make a wire with alligator clips on both ends. Clip one end to a good frame ground, and the other to your tank (a flange works well). If it is corrected, you can make the ground more permanent by attaching the wire to the flange with a screw.

mrfixit · Jul 3, 2008

weren't this gen's forward tanks poly? Mine was, but it's possible it was a replacement.

blacksnapon · Jul 3, 2008

mrfixit said:
weren't this gen's forward tanks poly? Mine was, but it's possible it was a replacement.

Good point! I'm usually working on stuff no older than 3-4 years old.

mrfixit · Jul 3, 2008

I guess either way, it can still be the grounding issue. Out here, I think the high lime content of our soil causes a lot of premature corrosion of the electrical connections.

Fellro · Jul 3, 2008

Those year trucks commonly have troubles with the sender wiper wearing out. My 88 just sits there and waves at me, on both tanks....

tomtoc · Jul 3, 2008

dumb question - where/what is the tank flange.

Its raining now, but I do think it is a poly tank. Still possibly a ground for the tank?

blacksnapon · Jul 3, 2008

tomtoc said:
dumb question - where/what is the tank flange.

Its raining now, but I do think it is a poly tank. Still possibly a ground for the tank?

The flange is where the two halves of a metal tank are welded together. If its poly, its a moot point. You'll have to attach the extra wire to the top of the sending unit.

Fellro · Jul 3, 2008

If it is a poly, most definitely a possible concern.

95F350XL · Jul 3, 2008

My front tank is metal sittin in a poly case. Its leaking out the side and I dont use it. I put a gal in and run it just to keep the pump good and the gas good.

tomtoc · Jul 4, 2008

I knocked on it - its metal. I'll try checking the ground later and let you know.

Lost · Jul 4, 2008

ALL I have had mine r metal with poly guard . Ran into very few ploy ones . Besides the aftermarket ones I put in. Wish they were .

tomtoc · Jul 4, 2008

looks like it was the ground - thanks guys. I hooked a jumper cable up to it and the frame rail and it fixed it. Will I hurt anything running it with a bad/no ground for a few days until I get back home

And, where is the stock ground? Should I clean it or just run a new one

mrfixit · Jul 4, 2008

Look at vince's original answer; His instructions are as good as it gets.

tomtoc · Jul 4, 2008

got it...so I can screw into the flange where the 2 halves come together?

Fellro · Jul 4, 2008

Stock ground goes right to the sender. It is riveted right onto the plate the fuel pipes come out of.

tomtoc · Jul 15, 2008

i finally got around to messing with this. i had some alligator clips on there, but i don't think they were getting to the metal (too much rust and plastic coating stuff). i took a wire wheel to the tank and the frame and cleaned them up real well. the clips seem to be working.

permanent - no. but i can use it for now. maybe someday i'll feel more comfortable about drilling through the tank to do it properly.

thanks again

mrfixit · Jul 15, 2008

I think the wire wheel was more hazardous than a drill, but to each his own.
The drilling we spoke of was through the flange, that flat protusion around the perimeter. If you drill closer to the outer edge, it shouldn't be a problem.
Take your time, be careful and use a center punch so your bit doesn't wander.

tomtoc · Jul 15, 2008

i thought about the wire wheel might be a little risky, but i did that to the flange as well. i didn't want to risk drilling the flange because my rear tank is still a little leaky. i didn't want 2 leaky tanks. i'd rather do one at a time.

tomtoc · Jul 23, 2008

well, the alligator clip fix lasted about a day then was happening again.

i tried to do it the "right way" with screwing through the flange and that didn't work either. here's a pic of what i did

wrapped wire around the screw, and screw into the flange
then on the other side, did the same thing to an existing hole in the frame. cleaned up around the hole a little bit to expose some more of the metal.

what am i doing wrong?

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