gas guage going crazy- 87 sub

[jonzcustomshop]

the fuel guage is going nuts in my 87 sub, right now it is stuck all the way full, but previously it would move up and down , stay at empty, then stay at full...
just nuts.

the sub did sit for 6 years, but the tank was on "E" when it got parked.

maybe varnish or something on the sender?
as far as I remember it worked fine when I parked it.

[munice]

you could have a bad ground, my gauge used to read full almost always... never a good thing, but i re-did some connections on the guage harness and it seems fine now.. also the float in the tank could be a bit corroded and have dead spots

[tucsonjwt]

There are a lot of threads on gas gauge diagnosis and fixes on this forum, so you could search for them. Someday we should have a tutorial for this issue, since so many people post about it. Everyone suggests checking the ground wire on the frame rail first, which makes sense - except it is not easy to reach. Usually, an erratic gas gauge turns out to be the sending units - but I recently replaced both my sending units in my dual tanks only to find out I had a bad gas gauge instead. In the future, after checking the ground wire, I will replace the gas gauge first ($50 expense), since it is a lot easier and quicker to replace the gauge than the sending units, and you might be able to sell the gauge or return it if it does not work. Aftermarket sending units (Spectra, $40-$50) will cause your gauge needle to bounce when the truck is driven, OEM AC/Delco won't ($140-!80).

[jonzcustomshop]

do you think a sender out of a diesel sub would work I have a good one of those, but this one is a gas motor.

[jonzcustomshop]

noticed today while driving, anything with electrical power makes it go to full -brake,blink, fuel injection..
if I let off the gas it would come down, then brake would jump it up a little , blink would make the needle blink, and giving it gas would make it climb to full.
would that denote a ground problem?

[Grease Monkey Kuztum]

I just bought an 84 that was converted from diesel to a 454 so the sending unit from a diesel should work? Im not 100% sure if tanks are the exact same but I imagine they are the exact same and its just the fuel door thats got a bigger hole for diesel nozzle lol spittin gas at ya when you fill up dangit, but from what it sounds like you might be getting a short somewhere in the wire and not just on the ground connection??? When you give it gas and the alternator kicks in to charge things it gets more juice and makes it go krazy then when let off gas and alternator kicks off it goes back to being a weak signal???

Not sure tho... I have the same problem tho on both tanks, so I think its my gauge but in the next couple days am gonna tear into it... If I find some easy trick ill post it up lol but nothings ever really easy so good luck lol