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TBI Starting Problem... HELP

Discussion in 'The Garage' started by stockk5, Aug 30, 2006.

  1. stockk5

    stockk5 1/2 ton status Premium Member

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    Hey guys, i just put another 350 in my truck, i hooked it all up, the timing was a lil off, went for a spin down the street. Started every time fine after that as well, just moving it aorund the yard. I came home hooked up the timing light to the battery, and the #1wire.. but i couldnt get it to work, so i just left it on there and went on to replace the kick down cable for the 700R. After that was all done, i went to start the truck up and it wouldnt start. It would turn over, try to start, but no fuel. My bro sprayed carb cleaner in it and it started up off of the fumes for just a second. Then wouldnt start again, i thought maybe it was the injectors that died. So i stole the tbi carb off my bros truck and put it on mine. Didnt work either. So now i have no clue what to do. There is plenty of fuel going to the carb,(i took the fuel line off and started it) just not getting sprayed down into it. I am now thinking the computer is messed up somehow. I unplugged the battery for about 10mins to maybe reset the computer but didnt work. Would it be the computer thats behind my glove compartment or another one? Anyone have a clue? sry for long post, this is just so frustrating being so close to having it done, then it dies on me. Thanks for any advice.!
     
  2. 1979jimmy350

    1979jimmy350 1/2 ton status

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    hook up a test light to the injector wires and have somebody crank it over. If it flashes that is good and means your comoputer is working. If it is not flashing you need to check a few things before you think about the computer. Make sure that the oil pressure switch is still plugged in you might have knocked it loose while doing the TV cable. Next take off you cap and check the restance on the pick up coil then test your ignition modual. My bet is on the pickup coil or modual
     
  3. stockk5

    stockk5 1/2 ton status Premium Member

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    so just take off the injector clips and use a voltmeter on them? How would the oil pressure sensor effect it from starting even when you have fuel in the carb it starts? thanks for the help
     
  4. 1979jimmy350

    1979jimmy350 1/2 ton status

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    the oil pressure switch is wire so that a engine with no oil pressure can not get fuel. if the fuel pump relay is not working right
     
  5. mrk5

    mrk5 The Sticker Guy Moderator Vendor GMOTM Winner Author

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    Go to the parts store and buy a test light. They're cheap, like $5-6. It looks like a screwdriver with a point. There'll be a wire coming out with an aligator clamp.

    You clamp the aligator clamp to a ground and push the point into the wire going to the injectors. It will blink while someone cranks the motor if the injectors are getting a signal. If no light, then your injectors aren't getting a signal. That means it's probably the comp.

    I believe you should also see fuel coming from the injectors while cranking.

    Are you sure the fuel in the line wasn't just residual pressure?
     
  6. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Sounds like your ignition module died on you man!

    The way TBI works, is that it pulses the injectors for every ignition spark that occurs, so if your distributer's module died, and it isn't sending a signal down the white wire, or not sparking at all, then the ECM will not pulse the injectors.

    The best way to test the ignition module is to turn the engine to top dead center on piston 1 by hand (take the plug out, turn the engine by the alternator stator nut, absolutely NOT the crank bolt, until you hear / feel air coming out of the hole, then set the timing mark to 0 degrees), put the plug back in, hook up your timing light to it (borrow one if you don't have one already) then turn the ignition to on, and quickly rotate the distributer back and forth until you hear it click as it fires on cylinder 1. You should hear the distributer click, one of your injectors click, hear the fuel pump run for 2 seconds, and see the timing light flash.

    If the fuel pump runs, but the injectors don't pulse, then your distributer module is fine, set the dizzy back to about 0 degrees by rotating it, and trying to center it on where it flashes, and tighten it down enough that it won't rotate when you start the engine, then go look at your injector wiring. You should have constant 12 volts on one pole for each injector. The ECM provides a grounding path to open the injectors.

    If you hear your injector pulse, but the fuel pump doesn't run, you need to check your fuel pump relay, making sure that it has a good solid ground, and 12 volts coming from the distribution block, not that it's fusible link is burnt up. In the fuel pump relay's case, the ECM provides 12 volts.

    If nothing happens at all, and your inductive timing light doesn't flash, then your ignition module is bad.

    If your ignition module works, along with the fuel pump, and there is no problems with the injector wiring, then you will need to try swapping your ECM out after you figure out what caused it to burn up the first time around. No point in putting another good ECM in just to kill it too, lol

    Oh, also check your fuses!
     
  7. stockk5

    stockk5 1/2 ton status Premium Member

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    thanks a lot for the advice, also where is my ignition module? thanks for helping the newbie at this stuff haha
     
  8. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Ignition module is under the distributer cap. It is the part that the electrical wires from the coil and the ECM hook up to :)
     
  9. stockk5

    stockk5 1/2 ton status Premium Member

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    well i put in a new ignition module, didnt work, its getting juice to the map sensor and to the injector clips.. so now i guess im gonna buy a computer to try to pull a code up.. any ideas?
     
  10. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Did you try twisting the distributer? Its never a good idea to just throw parts at an EFI setup, thats gonna wind up costing you a ton of money! You need to do some actual troubleshooting to figure out what the problem is
     
  11. 1979jimmy350

    1979jimmy350 1/2 ton status

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    you do not need a computer to pull a code, just a paper clip, jumper the termainals and count the flashing light. it will throw a code 12 3 times then any code that is in the ECM 3 time then if its done it will show code 12 again. By code 12 i mean flash pause flash flash pause then repeat
     
  12. stockk5

    stockk5 1/2 ton status Premium Member

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    well we got the right tool and the sensors for the injectors arent pulsing.. i had a shield for my starter and i think someone said it shorted out my computer or the fuseable link to my computer which in turn burned up my computer. is there a way to test the computer outta the truck? where do u get replacements?
     
  13. stockk5

    stockk5 1/2 ton status Premium Member

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    anyone know if i can test the computer outside the truck? how do you go about doing this? sry for a lotta questions i just havent driven it in months, and reallllly want to haha.
     
  14. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    I don't know if a place like Blotto Zone can test an ECM or not, but you can always ask them.

    http://www.autozone.com/in_our_stores/free_testing.htm
     

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