Re: gas guage stuck - advice? (archive)

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Firstly, the sender unit was a mongrel to detach from the top of the tank! When you finally get it off, you find the fuel is sucked up a copper(?) pipe that runs all the way to the bottom of the tank. This runs in conjunction with a very thin rheostat-type wine, a float, and various sensors that operate the gauge and the white warning light. The whole affair is enclosed in an aluminium tube, which looks rather crude, and is all held together by a single screw at the very bottom centre of the whole apparatus. The tube is, incidentally, about the same diameter as the sender top itself, as you look at the tank inside the trunk.

When I took mine out, (and a tight fit it was) it seemed that the aluminium sleeve didn't seem to sit properly on the underside of the fuel tank seal. What I eventually discovered was this. The clearances in the tube seem quite narrow - unless the whole apparatus fits together neatly, then it's not "square" inside the tube, and the float will stick. The reason seemed to me as follows:

The very base of the whole apparatus (near the bottom of the fuel tank) is made of a plastic-like material. Through this baseplate protrudes not only the thread for the screw that holds the whole assembly together, but also the small hole for the intake pipe itself. After all, you've got to get petrol/gas into an otherwise sealed tube somehow. The intake pipe protrudes through the hole in this 'plastic baseplate' only to the point where it's flush with the bottom.

BUT, it seemed to me that the plastic baseplate had somehow swelled over the years, making the hole for the intake pipe too small. This seemed to cause just enough distortion in the entire length of the unit (which must be 18 inches long) that it interfered with the smooth operation of the float (hence sensor).

I reamed out the hole a bit so the pipe was not obstructed, then the whole assembly fitted back together much better, and was able to be reinserted in the tank without disturbing the insides. Buy a new gasket for the tank-top, by the way - they're still available (at least in Australia) and aren't expensive. Unless, that is, you like the smell of petrol wafting through the car! When you re-assemble the whole unit and wave it about, you can hear the float sliding up and down its rheostat wire. If you pull the whole thing out of the fuel tank, and it seems to slide OK - I'll bet that if you put it back it will stick again! In other words, you very actions in removing the sender unit have temporarily freed the obstruction - but if you don't find what caused the problem it will happen again.

I'm assuming, of course, that your problem is at the sender. I guess if the gauge itself was the problem, it would just be reading empty.

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