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Fuel Sending Unit Cheap Fix?

Discussion in 'The Garage' started by prossett, Oct 22, 2005.

  1. prossett

    prossett 1/2 ton status

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    Besides changing in a new unit, is there some neat trick to fixing it?

    Something like take it out, shake it all about and get someone to blow it hard, and off you go...?

    ;)
     
  2. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    all depends, what is the problem?
     
  3. prossett

    prossett 1/2 ton status

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    The gas gauge stays up past the full mark (say, 2 o'clock position) and occasionally when braking or turning left it goes down to almost empty and then comes back up.

    I've checked the ground wire from advice on the site, and nothing changed. Pity, it was a good simple fix.

    I go out into the desert a lot and an accurate gas reading is crucial. I write down the mileage at every fill-up, but it's not good enough.

    Since the gauge does move somewhat in synch with braking and turning I suppose the gauge is alright and the problem is in the sending unit, which is not completely toast, just a bit confused and needing some discipline.

    BTW, I'm new to GMC so all I know is what I read here. :D
     
  4. blazerguy 90

    blazerguy 90 1/2 ton status

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    It sounds like your sending unit is shot, I just changed the sending unit and fuel pump on my 90 Blazer last weekend, its not as hard as it looks and you can do it in a day. I got the sending unit from LMC Truck.
     
  5. beater_k20

    beater_k20 Banned

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    are you sure you're trying to fix a fuel sending unit there? :confused:
     
  6. prossett

    prossett 1/2 ton status

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    I guess the taking it out, shaking it all about and then the blowing could be confusing... :haha:

    Yep, fuel sending unit. As far as I know, it tells the gauge how much fuel is in the tank, and that's not happening. It could still just be the gauge itself, but the needle does move around somewhat reflecting what's happening in the tank, so it doesn't look like an electrical problem.

    I'm just plain guessing, since it's my first GMC and the repair manual hasn't arrived yet.

    Is it some kind of float mechanism with sensors?

    I was just hoping there was some simple fix that I could try before replacing the unit.
     
  7. beater_k20

    beater_k20 Banned

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    yes, that's exactly what it is. check the ground terminal on the tank. remove it, and ground it to the frame. it should spike the guage in the dash. that will tell you that everything in the system up to that point is good. if it does spike the guage, drop the tank, replace the sender, and be on your merry way. oh yeah, run it REAL low on fuel before you try to drop the tank.
     
  8. HarryH3

    HarryH3 1 ton status Author

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    It's a float on a long, wire arm, that is attached to a 90-ohm wire-wound rheostat. As the float rises and falls, the resistance of the circuit changes. If you're lucky, you may be able to take it out, clean the contact area and then slightly bend the wiper arm so that it makes better contact with the wires in the core of the rheostat. It isn't fun to remove the tank, but the job isn't too bad if the tank is near empty when you start. It's worth a try to fix it, as a new one costs nearly $400 US. :eek1: :eek1: :eek1: :eek1: :eek1:
     
  9. Tra 23

    Tra 23 Registered Member

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    I had a similar problem with my 88 K5. When I removed the tank I found that the plastic baffle had come loose from the bottom of the tank and was up against the float. I had to use fender washers and pushnuts to re-attach it. Works great now.
     

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