gas gauge don't work

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Nov 28, 2010 | 05:29 AM

334eagle

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gas gauge don't work

i have a 1981 ford f100 with the dual tanks an just yesterday the dang fuel gauge quit workin. any body out here got any clues as to what i should check? i took a ford wrench (rubber mallet)to the transfer valve on the frame rail an beat on the forward fuel tank thinking something may have been stuck an the fuel gauge started to move then it just quit an returned to the walk position. i looked in the haynes shop manual for some tips an they were real vauge.
the fuel transfer vale i don't think has been workin properly for a while cause when i fill up both tanks the rear tank would just feed in to the front tank , man i thought someone was stealin my gas. i'm thinkin maybe this might have something to do with it . hell i don't know.
any help this direction sure be apprecitated
thanks,
bubba earl

Nov 28, 2010 | 07:18 AM

smashclash

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From: South Jersey

definitely the fuel selector valve is shot if it's moving fuel between tanks. But is your fuel gauge not working for both tanks or only one? If it's only one it's probably the sending unit in whichever tank it's not working.

Nov 28, 2010 | 04:02 PM

Eddiec1564

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From: Arcadia, Fla

The brass floats(sending unit) with fill up with gas causing them to sink giving you a empty reading. Have to drop the tanks to check them out.

Nov 28, 2010 | 06:18 PM

Wicked Endings

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From: Richlands, NC

Quote:

Originally Posted by Eddiec1564

The brass floats(sending unit) with fill up with gas causing them to sink giving you a empty reading. Have to drop the tanks to check them out.

And that is no fun at all.

Nov 28, 2010 | 10:08 PM

ctubutis

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From: Denver Metro Area, CO

Could also be the rheostat in the sender has finally worn through and broken, you need to
pull the sender and remove the triangular cover to see this failure.

Nov 28, 2010 | 10:13 PM

kermmydog

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From: Western Central NV

If the 81 is the same as the 86 the sending unit & pump are a unit. I had to replace mine as a unit a few years ago because one tank the gauge quit working.
Craig

Nov 28, 2010 | 10:19 PM

1986FordF150I300

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From: San Antonio, Texas

Quote:

Originally Posted by kermmydog

If the 81 is the same as the 86 the sending unit & pump are a unit. I had to replace mine as a unit a few years ago because one tank the gauge quit working.
Craig

Pretty sure a 81 wouldn't have a pump in the tank seeing how efi for these trucks came later on hehe

My 86 has the sending unit and pick up lines in one unit on each tank. If you handy with soldering u may be able to pocket sum rheostat's at the j/yard from a newer truck (can't recall up to what year but i know some 90's use the same rheostat) and then pull your sending units out and solder on the new rheostat in place. Not that i imply stealing anything

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Nov 29, 2010 | 05:04 PM

Eddiec1564

Cargo Master

Joined: Mar 2007

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From: Arcadia, Fla

The 80 to 86 also have a reverse resistance than the 87 and up sending units. If you swap out a 87 newer sending unit your guage will read empty when full and full when empty. I found out the hard way when I converted my 84 F250 to EFI. Had to do some re-engineering and use the 84 sending unit in a EFI assy.

While I had all that apart I did find the brass float starting to fill up so I repaired(solder the holes) it only to have it fail about 2 months later! I wound up makeing a new float from a car which had the foam floats for the sending unit.

Nov 30, 2010 | 10:03 PM

#10

1986FordF150I300

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From: San Antonio, Texas

Well Eddiec, glad you told me that, i had pulled some rheostats out of a newer truck a while back but hadn't got to putting them in yet. Looked the same as my current ones but now i know not to do that. Though i guess a backwards working guage is better then a non-working guage lol.

Tell your friends that the more you drive, the more gas you have lol.

Dec 1, 2010 | 05:02 PM

#11

cole45

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be sure to test your guage first. if you unplug from the tank your gauge should go all the way to one end of full or empty. be sure to have the key on. next grounf out the wire. the gauge should move to the other end. have seen in the pass the wire come out of the instrument panel plug. if the gauge is working properly then it has to be your sending unit in the tank. the selector valve is shot for sure as others have said.