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Testing a TBI injector

Discussion in 'The Garage' started by 6.2puller, Jan 19, 2006.

  1. 6.2puller

    6.2puller 1/2 ton status

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    how would you go abouts testing a TBI injector to make sure it is good?
    I got a TBI motor in my brothers buggy that has fuel at the back of the throtle body and at the regulator but nothing sprays. Their is 12 volts at both of the inner injector wires, as in one side of each injector when the ignition is on but we are not getting fuel out the injectors. The motor ran fine until it sat for a month or two and now it will only run on either but will not spray fuel to run on its on.
     
  2. Thunder

    Thunder 3/4 ton status

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    The ECM grounds the injector to make it fire. Have you checked the fuses.
    Try cleaning the plugs at the distributor and coil. if the ECM sees no spark it will not fire the injector.
     
  3. readymix

    readymix 3/4 ton status

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    Pull the connector from the pick up coil off of the ignition module, then use a noid light connected to the battery on the clip end......then alterneta touching the leads on the ignition module with the noid light.

    Every time you hit a lead on the module it will fire the hall effect device in the module and the ECM will fire an injector. If it does not it could be any of the following
    1. Module
    2. Computer
    3. Wiring
    4. Injector
     
  4. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    i had a problem after installed the motor for the 3rd time, it tured out to be we forgot to put the bolt in the back side of the head that grounds the harness, put that on and we had fuel.
     
  5. sled_dog

    sled_dog 1 ton status

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    sure there is fuel pressure? No fuel no spray
     
  6. mouse

    mouse 1/2 ton status

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    The fuel issue is what I am currently chasing on my newly-converted to TBI, 350. I can only start if I give a little gas in the TBI, but it seems to run perfectly after started. While cranking it does not spray any fuel.

    So far I've swapped the MAP with a couple of spares, and rebuilt the TBI/fuel regulator, but still the same problem. Tonight, I'll drop the tank and replace the pump.
     
  7. 6.2puller

    6.2puller 1/2 ton status

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    I have been searching around and someone else had your problem. It turned out to be that the ECU was dropping down to 7V under cranking then jumped up to 9.6V once running. 7V was apparantly not enough for it to run.
     
  8. 6.2puller

    6.2puller 1/2 ton status

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    We Pulled the line at the back of the TB and it had fuel, then we pulled the injector risser and cranked it and the regulator "bowl" filled right up fast. Not sure how you can check pressure on these other than that since their is no Schrader valve like the other injected models.
     
  9. 6.2puller

    6.2puller 1/2 ton status

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    Will try this this weekend, thanks.
     
  10. beastofablaze

    beastofablaze 1/2 ton status

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    Mine are just dumping fuel into the manifold... this was after I forgot to hook my ground to the frame and fried my ecm hooking up my battery. Thing is I think they might have blown from too much fuel pressure before I fried the ecm. Is there anyway to check?(I have a new ecm now)

    *hijack over*
     
  11. HarryH3

    HarryH3 1 ton status Author

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    Make sure that the ECM power is connected to the proper place. There's one feed that must have 12 volts at ALL times. Another must have 12 volts in RUN and in START. Most power feeds in the truck switch OFF in the START mode. If you have your ECM wired to one of those, the ECM won't work until you let the switch come back to RUN. :rolleyes:
     
  12. HarryH3

    HarryH3 1 ton status Author

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    6.2Puller - Do you have a spare ignition module that you can swap in? If the module isn't sending ignition reference pusles to the ECM, then the ECM won't fire the injectors.
     
  13. mouse

    mouse 1/2 ton status

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    Good idea, I'll double check, but I installed a second fuse block just to run the FI. Still, I gotta check.
     

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