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TBI won't start

Discussion in 'The Garage' started by WinslowS, Dec 11, 2006.

  1. WinslowS

    WinslowS 1/2 ton status

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    I drove my truck to work today, and when I got off, it would not start. It is a 1989 V1500 Blazer TBI 350. The motor turns over, but its not getting any fuel. When my dad sprays starting fluid into the Throttle Body it will start then die immdiately. We think its an electrical issue, maybe with the fuel pump or the computer not telling the injectors to inject? Anyone ever had any similar problems or any ideas? We are about to run back up to it to check it out with a multimeter.
     
  2. Slapperbar

    Slapperbar Retired Navy NDT Examiner Premium Member

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    Fuel pump relay?
     
  3. GotLabs

    GotLabs 1/2 ton status GMOTM Winner

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    Or fuel pump. Did you try beating on the tank and see if it would start? If it does, your pump is shot.
     
  4. jamber2541

    jamber2541 1/2 ton status

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    Check your ignition module, it also controls the spark to the injectors. Take it off and take it to any half decent auto parts store they should be able to check it for you
     
  5. 1979jimmy350

    1979jimmy350 1/2 ton status

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    It could be a bunch of things, first off we can figure that you have spark so cross that off the list, There is a test lead in the engine bay leadingto the fuel pump, put 12V to that and see if the Fuel pump runs, if it does then make sure that you are getting fuel to the throttle body (if not look at fuel filter) then hook up a test light to the injector to check for injector pluse, if you are not getting pluse then get the distributor modual tested, just make sure they test it a few times in a row, the machine don't put the modual under a real load, i have had moduals in the past test good and they were bad. If all that stuff checks out post back up and well go from there
     
  6. k20

    k20 3/4 ton status

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    turn key on, listen for the pump priming the system, if it runs the pump & the relay are fine.

    If not, run a wire from the positive post of the battery to the, IIRC, red pigtail that is coming out of the fuel pump relay. That will bypass the relay and send 12v straight to the pump, if it runs the pump is fine, the relay is dead. If it still doesnt run then either the pump is dead or the wiring is screwed up (melted, chafed, etc).

    If the pump runs, it could be the ignition module or the temperature sensor in the intake manifold (stuck on hot, so it is giving it really no fuel, I had basically this same problem).

    Plug in a NOID light to the wiring for the injectors, if its pulsing weak then I would say the temp sensor, if no pulse, then the ignition module.

    Might also be the oil pressure switch on the backside of the block, next to the distributor, but I think that kills spark, not fuel.
     
  7. WinslowS

    WinslowS 1/2 ton status

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    My dad and I just got back from trying to get it to start again. No luck. We tried bypassing the relay for the pump without any success, but we don't know if we had a good connection. We tried the test module too, with no luck. We used the multimeter and didn't get a reading off of the relay, but the fuse was fine. We replaced it just to make sure and still nothing. We are gonna go back tomorrow after work with my dad's electrical tool kit and try to bypass the relay again, and check out some of the suggestions from yall.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    You don't need to "bypass" the relay any other way than bringing some good wire with you, and hooking it to the test lead hanging off the relay connector. I didn't see you mention it, that will save you some time and effort.

    I *believe* you can force it to run off of the ALDL connector in the cab and it would only take a paperclip, but I won't swear to that. I believe it's been posted before though that it is possible.
     
  9. CB77GMC

    CB77GMC 1/2 ton status GMOTM Winner

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  10. WinslowS

    WinslowS 1/2 ton status

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    Cranked right up after work tonight, had my tools and everything. Probably a bad fuel pump so once this tank is empty I will drop it and replace that.
     
  11. WinslowS

    WinslowS 1/2 ton status

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    Annnnnd it won't start again, was almost late for school and when I get home still won't crank, banging on the gas tank didn't help. I think I am gonna have to siphon out the 20+ gallons in her and drop it tomorrow to replace the pump. Anyone know of any good write ups on how to do this as my Haynes Manual deems this to be below the abilities of the average mechanic and tells me to take it to a shop.
     
  12. Mastiff

    Mastiff 1/2 ton status Premium Member

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    This is where you decide whether you'd rather go through the torture of dropping the tank, or cut an access panel in the bed. :wink1:
     

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