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Gas Tank Question

Discussion in 'The Garage' started by Justin Fleming, Sep 7, 2005.

  1. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    when I fill the tank up, the gauge shows way past full.....Is there a way to adjust this correctly so that E = empty and F=full??

    thanks

    Justin
     
  2. cbbr

    cbbr 1 ton status GMOTM Winner

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    If mine actually gets to "E" its way too late. Mine does the same thing, i have no idea if it is worth the time/effort to fix, but will be interested to see... :ears:
     
  3. 73k5blazer

    73k5blazer Unplug the matrix cable from the back of your head Premium Member

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    It's an easy adjustment, just don't fill it up so high! :rotfl:

    Sorry couldn't help it. I don't there there is a way to adjust, at least the GM Service manual doesn't outline a way, and looking at one out of the IP, it doesn't really look like it. You can get a different gauge, they are a couple of bucks at the boneyard.
     
  4. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    anyone whith ideas...
     
  5. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    I noticed mine when I bought the truck . It could go from past Full to Empty . Well after the first time I pushed the truck to the gas station when it was just above Empty , I make sure I gas up before 1/8th of a tank left .

    Cheapest fix is to remove the needle , but then it goes too far the other way :wink1:
     
  6. dyeager535

    dyeager535 1 ton status Premium Member

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    It's likely a sender issue.

    If I'm not mistaken, "full" corresponds to high resistance (90+ ohms) while empty is essentially 0 resistance.

    If it reads "E" ok, and has a fairly accurate travel other than reading full way too high, I'd suspect the rheostat on the sender is not in good shape.

    There is a procedure for cleaning it up on here. I did that with mine (gauge read overfull and over empty) and got it to MUCH closer than it was. Still not perfect, but a heck of a lot cheaper than buying a new sender. (TBI)
     
  7. sope

    sope 1/2 ton status

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    The only adjustment is to bend the sender float rod. This is kinda hit and miss to get it right. If you do take it out I would recomend cleaning the resister with contact cleaner.
     
  8. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    where is this resister located?? In the dash or in the tank??

    thanks
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    Well there is a resistor on the back of the gauge, but that seems to be a fail/no fail problem. Someone on here had one go bad on another gauge, and posted up about it.

    I don't know as the thing in the tank can be called anything other than a rheostat. It's a very thin wire wrapped around a non-conductive piece on the sender.
     
  10. sope

    sope 1/2 ton status

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    In the tank on the sender unit. You will see it at the base end of the float rod. Cleaning this probably won't fix the problem but you should spray it while it's out.
     
  11. sope

    sope 1/2 ton status

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    I guess I should have called it a rheostat or variable resistor. That's the thing I meant.
     
  12. spearchucker

    spearchucker 1/2 ton status

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    Someone should do a write up on the fuel gauge not reading right and how to diagnose it. Hint, hint.
    First of all, don't go bending the sending unit float arm. Why would you have to do that, it's a fairly stiff piece of metal and gas sloshing around isn't going to bend it. The only reason it would get bent is if someone else already bent it, which is highly unlikely. Fix the real problem.
    Disconnect the plug from the sending unit, it's near the gas tank on the driver's side along the framerail. There are 2 wires, one for the fuel pump (if you've got an in tank pump) and the other is the sending unit wire. I forget which color wire is for what, but you can figure it out. With a volt meter, stick a probe in one of the sockets of the plug. Have someone turn the key to accessory, and for a few seconds the one of those connectors will read 12V. You are interested in the other wire, which would be the sending unit wire. Short this wire to the frame, and with the key in the accesory position the gauge should read either full or empty. Un-short the sending unit wire and it should read the oposite. This will tell you if the gauge is reading correctly or not. If it reads correctly, then the problem is the sending unit. More than likely it's been tarnished from the gas. You'll have to drop the tank, take the sending unit out and carefully clean the windings as Dyeager said. I think you can use some very fine sand paper or wet/dry sandpaper. Also make sure the wiper on the rheostat is making good contact throughout it's motion, if not gently bend it so it does. You can also check the sending unit with an ohm meter connected to the plug on the sending unit. It should read from 0 to 90 ohms. Or you could spend a couple hundred on a new sending unit.
     
  13. raptorparts

    raptorparts Registered Member

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    And don't think a new sending unit is a cureall either. Purchased a new one over from my local chevy dealer and it's never read right. Upon close inspection, you can see where the needle is sticking on the sending unit and mine never reads over half tank. I've dicked with this several times and i'm far from a dumbass but i haven't found a way to make it work right. waste of money......
     
  14. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    thanks for the great info
     
  15. dyeager535

    dyeager535 1 ton status Premium Member

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    Yes, once the sender is pulled you can check resistance (or even gauge operation) by hooking it up external of the tank. Of course that doesn't mean it will read right when the tank is actually "full" but you can probably get a fairly good idea.

    I used 0000 steel wool on the rheostat on mine, contact cleaner didn't make a difference on mine. Have to be VERY gentle though, the wire is not real tough. The wire on mine had a nice black coating that I was able to remove.

    Want to make sure all the steel wool particles are cleaned off of course.
     
  16. Justin Fleming

    Justin Fleming 1/2 ton status Premium Member

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    I tackeled it tonight

    Well for my gas tank problem I started in the dash. Today I noticed that if I tapped on the gauge in the dash it would bounce around. So I pulled the dash apart and man some one has realy messed things up behind here. Anyhow i pulled the gauge out of its socket and I noticed some rust and corrosion. I also notice one wire on each terminal that was sodered to the terminals but appears some one has cut the other end off. I am unsure what was going on in there. But after a little sandpaper and some fidgiting around with it it seems to read full correctly.......I will have to drive a few miles to confirm that E is correct.
     

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