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gas gauge gone crazy....help

blazin_blazer

1/2 ton status
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central arkansas
my 96 tahoe has been sitting for about 6 months, with the tranny shot in it. it has the 4L60e in it and the place i'm taking it to wants 1350 to R&R and rebuild it while its out(new tq converter). it seems reasonable b/c most other places want $900 or so w/ only a 60-90 day warranty. the guy wanting $1350 where i'm taking it, gives a 2yr/24000 mile waranty on the rebuild so , i feel better taking it to him, since he's willing to stand behind his work...

but i've had a few people talk bad about the place, saying, ''if you go there, you'll need that warranty'', while i have a friend who had his trans rebuilt there 3-4 months ago, and he says he's had no trouble and he is ROUGH on his truck! plus this shop is clean and neat, he builds trannys for sled pullers, mud boggers, and dragsters, he has his own dragster sittin in his shop, as does his son. i figure w/the warranty and the rigs i've seen in his shop, and the way his shop looks, compared to all the other tranny shops i've visited that look like they haven't had a clean up in 2-3 yrs, not even a sweep up, i'm going to this guy and paying the extra $400 for the warranty, b/c i've found out, if you talk to enough people you'll find someone who will bad mouth any & every shop there is!

i finally get the cash together, i go to take it to him, so yesterday, get in and of course my yellow top is dead, so i try to jump it...no go after leaving the good battery/vehicle hooked up while it was running for 1/2 an hr. so now my yellow top is on my gel cell charger. but, while i had the jumpers on the truck i noticed something weird. when i parked the truck, everything worked just fine.

but when i had the jumper on it yesterday, i turned the key and it tried to turn over, but not enough juice. thats when i noticed, my voltage gauge was up to about 13-14v. oil pressure 0psi, water temp pegged on downward peg,(normal), but the gas gauge is pointing at 3 o'clock, thats about 1/2 the gauges full sweep past the full mark. now i'm worried someone may have filled me up w/ water or something else, just to be malicious. any ideas? how can i check the sending unit to see if it has just went bad? any other ideas? should i not start this thing until i figure out the fuel gauge? anyone else ever had their fuel gauge do this in a mid 90's truck or tahoe?
 
I don't think the gas guage can read too full because there's extra liquid in it (water or gas). More likely is that the wire came off or it is grounded on something.
 
The gas gauge reads empty when there is full current going to the gauge (ie, all 12-14v) and full at a certain amount of resistance. (I think 0 ohm for full and 90 ohm for empty)

The gauge has two "grounds" one for the unit, and one for the signal. You have lost the "signal" ground, so the gauge has no "limit" so goes way past its full mark. Find the problem with the signal ground wire and you will fix your problem.
 
thanks for the replies guys, i feel better about starting this thing now. i will have to track down this ''signal'' wire...any idea how its routed? does it go to fuse box or the computer is what i'm mainly asking. again thanks for the replies!
 
GM grounds a lot of its chassis circuits to the engine, and since your mechanic was working on the tranny, look around there. Something similar was the cause of a gauge reading high on a van I worked on.
 
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