Fuel gauge issue

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Jan 27, 2016 | 12:28 PM

401tonyo

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From: chepachet ri

Fuel gauge issue

The truck is a 1981 f-100 flairside with 16 gal. tank. Two years ago the sending unit was replaced.Worked fine for a couple of months. I did the conventional troubleshooting test(ground feed wire etc.),and determined it to be a faulty sending unit. New unit installed, turn key on gauge moves about a sixteenth of an inch towards full. Remove sending unit from tank plug in connector and manually move float arm,and it registers on the gauge.What am i missing? There is fuel in the tank,and i tried running a separate ground to the battery. I am stumped,any ideas? thanks

Jan 27, 2016 | 12:30 PM

Rusty_S

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From: Houston

Never mind I reread your post said it works out of the tank. Also see you ran a separate ground and still same thing.

Is the float new? If its used does the float feel heavy?

Jan 27, 2016 | 12:45 PM

401tonyo

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From: chepachet ri

Thanks for the reply. The sender is new, but it has a plastic float as opposed to the brass one that was on the old unit.

Jan 27, 2016 | 12:47 PM

Rusty_S

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From: Houston

long as the plastic does not feel heavy then that can not be it. Plastic even solid plastic floats will over time absorb fuel and become heavy and wont float.

I had that happen on a '68 Ford 3000 diesel tractor it would work some times and some times it would read E as the float was super heavy from years of soaking up diesel fuel.

Jan 27, 2016 | 12:58 PM

401tonyo

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From: chepachet ri

Yes i could see that happening,but this float is new. But you have given me an idea. when the weather warms up i will put the sender in a pan of gas and see if it does infact float. thank you.

Jan 27, 2016 | 01:36 PM

kr98664

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Quote:

Originally Posted by 401tonyo

Yes i could see that happening,but this float is new. But you have given me an idea. when the weather warms up i will put the sender in a pan of gas and see if it does infact float. thank you.

How much effort does it take to move the sender arm? If partially binding, it could be the "lift" provided by a perfectly good float is not enough to move the arm when installed in the tank.

That's a good idea to submerge the float in a container of fuel. Just do it with the float attached to the sender arm, to make sure the arm can move freely.

FWIW, I prefer plastic floats. Brass ones eventually corrode. Cork floats (giving away my age here) eventually get heavy and sink. Plastic floats seem to hold up best of all.