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Removing TBI

Discussion in 'The Garage' started by 87GMC, Feb 26, 2005.

  1. 87GMC

    87GMC 1/2 ton status

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    I swapped in a ZZ4 crate motor and tried to keep the TBI, but it just doesn't run right. I changed to a carb but I'm still using the intank pump. Which wire at the fuel pump relay is the power supply? Also which wire at the distributor is the power lead? Has anyone else removed a TBI setup? How hard is it to separate the TBI wiring and leave everything else?
    Thanks
     
  2. dirtwarrior17

    dirtwarrior17 Banned

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    there is a plug that goes into the gas tank.... it sits on the driverside at the back of the truck and should be sitting on the frame right about where the gas tank starts. Just unplug that and your power to the pump is cut.
     
  3. 87GMC

    87GMC 1/2 ton status

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    I don't need to cut power to the pump. I need to supply power to the relay. I'm keeping the pump and using a regulator, but removing everything else TBI related.
     
  4. dirtwarrior17

    dirtwarrior17 Banned

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    I'm confused:confused: :confused: :confused: you ran it with the tbi but you didn't have power to the relay? Is that even possible?
     
  5. 87GMC

    87GMC 1/2 ton status

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    When I ran it with the TBI, I used all the factory stuff. Now, I removing the TBI and computer but keeping the intank pump and relay. The computer used to send the power signal to the relay. I need to know which wire at the relay recieved that signal from the computer so I can run my own power wire.
     
  6. Fierospeeder

    Fierospeeder Banned

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    i have to look at a wiring diagram. or someone can post one up on here.


    You might be able to get away with the way GM designed their fuel pump circuit. When oil pressure is sensed, the fuel pump is powered.


    Usually, the ECM grounds the relays. So you could remove the ground to the ecm from the relay. Ground it to the chassis. Then run a hot wire from the ignition key on with a fuse in series to the relay.
     
  7. Fierospeeder

    Fierospeeder Banned

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    I reread your question.

    There are four wires (usually) at the relay.

    remove the relay and if you have a test light or multimeter, you can narrow down the wires.

    Turn the key on and one of the wires should be hot. That is the wire going into the relay and connecting with a 2nd wire with the same gauge(size) going to the fuel pump.

    Usually, the ecm wires are thinner. So look for the two thin ones. The ground is usually black/white.

    I found a wiring diagram. It should be close to you truck. You need acrobat to view it.

    http://olympiafj60.home.comcast.net/TBI_wiring_diagrams.PDF
     
    Last edited: Feb 27, 2005
  8. 87GMC

    87GMC 1/2 ton status

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    thanks for the help
     
  9. Thunder

    Thunder 3/4 ton status

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    If you are going to run the stock in tank fuel pump you must have a return line back to the tank. If you dont the fuel pump will overheat anf fail in a short time. You can get regulators made with a fuel return port.
    Also cant use the TBI dist it is computer controlled and has no mechanical advance.

    All you really needed to do to keep the TBI and make that motor run right was get a new chip burned for the computer. Might have been cheaper than converting to a carb.
     
  10. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    You can put in the ZZ4 , why not work the injection bugs out ? I would think it could be done with some of the members here helping you :)
     
  11. 87GMC

    87GMC 1/2 ton status

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    The regulator I bought had a return port, so that shouldn't be a problem. The motor came with an intake and HEI dist, so my only expense was the regulator. I had the carb already.
    I wanted to keep the TBI, but I can't find what is wrong with it. The motor idles fine but stumbles all over itself when driving. Acts like the firing order is wrong. I've checked that and also the timing, but both are fine. We've tested each part of the system and it checks out fine. It just won't get up and go:(
     

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