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fuel guage not working...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by reddog64, Feb 10, 2002.

  1. reddog64

    reddog64 1/2 ton status

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    OK... I really hate not knowing how much fuel I have... it really sucks...

    I thought it was the guage itself... so i popped out the old guage... put a new one in...
    I set the guage... moved it with my finger... to full... i turned the truck to run.. the guage went to empty... so the guage is fine... I flipped the tank switch... did the same thing went to empty... Supposedly the floats are fine... anyone know about the wiring with dual tanks on these trucks... really need this to work...
     
  2. 90K5

    90K5 1/2 ton status

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    On my 90, it has an electric fuel pump...don't know what year you have, but if my pumps loses its ground, the gauge will do wierd things, but the truck also won't start...I'm thinking a bad sending unit is the problem.

    90K5
     
  3. reddog64

    reddog64 1/2 ton status

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    it's a 1978... mechanical pump...
     
  4. chevyracing

    chevyracing 1/2 ton status

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    If the gausge goes to full when the tank is empty it is the ground, if goes to empty when the tank is full it is the power usually. The sending unit is basically a rehostat. If the rehostat gets "varnished" by the fuel it is not making contact with the pickup. It sounds like that is the problem if you have power to the gauge. You either need to replace the sender or get some electronic cleaner and take the sender apart and clean it real well, personaaly I would replace the sender.

    John

    Like to go sloppin' 'round in da mud in a rapid fashion....=)

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  5. muddin4fun

    muddin4fun 3/4 ton status

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    I had a similar problem once. The headers had melted the insulation off the wire that went from the tanks to the guage and it was grounding out.

    <font color=green>Can't sleep...the clown will get me</font color=green>

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  6. Chevit

    Chevit 1/2 ton status

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    Mine works fine when it is dry out, but once it starts raining it jumps all over the place. I first thought it might be the float but that would not have anything to do with the rain so I am thinking it could be the connections on the top of the tank. What do you think?

    84 K5, Crate 350, 700r tranny, 3.73 rear, 32 11.50 15, Q-jet
     
  7. HarryH3

    HarryH3 1 ton status Author

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    GM fuel senders have a range of 0 to 90 ohms. 0 ohms in the circuit will cause the gauge to read empty, while 90 ohms will cause it to read full. So reading empty all the time implies that the wire between the gauge and the sender is grounded out somewhere along its path.

    If the gauge reads way past full all the time, then you're looking for an open somewhere in the circuit.

    <font color=black>HarryH3 - '75 K5</font color=black>
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