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Fuel problem

Discussion in 'The Garage' started by pomai, Apr 3, 2007.

  1. pomai

    pomai 1/2 ton status Premium Member

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    While trying to start the motor, fuel begins to spray continuously out of the injectors like an umbrella while the motor is turning over, and stops when the key is released.

    Could I have installed the chip incorrectly? or could the fuel pressure be to high? approx 14 psi. Theses injectors were rebuiled by CFM Tech and performed perfectly before installing this new motor, 383. All I did was transfer the injectors & injector housing onto the new bored throttld body.

    Thanks, Ed
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    You can try re-seating the chip if you messed with it, but doesn't sound like the issue.

    Make sure your injector leads aren't shorted to ground, maybe they got pinched in the swap? Even that doesn't seem like a plausible explanation, but it's free to check.

    Coolant temp sensor is hooked up and working right? Might simply think the engine is very cold and dumping an insane amount of fuel for cranking.
     
  3. Jason4x4

    Jason4x4 1/2 ton status

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    If you took the injectors out and transfered them, it sounds like you pinched the o ring on the bottom of the injectors, so as soon as the fuel pressure builds up, it just goes straight in.
     
  4. loafer

    loafer 1/2 ton status

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    The injectors are suppose to fire while cranking. If they were leaking they would contiue to leak after you release the key until the fuel pressure dropped to atmospheric.

    Does the engine start and run?

    Did I misunderstand what you were asking:confused:


     
  5. vortec

    vortec 1/2 ton status

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    yeah, i'm not really hearing a problem, here. what did they do differently before the chip? starting a cold engine takes a rich mixture so the injectors have to dump plenty of fuel, just like pumping the petal before starting a carbed vehicle.

    14psi is on the high side, but shouldn't be a problem. 9-13psi is what gm tbi systems need, stock.

    a conical spray pattern is correct, btw. so, your "umbrella" pattern could be right, as long as it's staying atomized and not just spraying straight into the walls of the throttle bores and collecting as liquid.
     
  6. pomai

    pomai 1/2 ton status Premium Member

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    The fuel was just spraying out continuously in an unbrella like patern. I've never seen it like that.

    No, the engine didn't start.:mad: I pre lubed the motor, installed the distribotor, conected the wires and tryed to start it, but it didn't start.
    While turning the motor over the service engine light blinks. I need to check for spark. I am getting power to the coil via the pink wire. I instaled the coil on the fire wall, could this cause a problem, like inproper grounding of the coil? I was going to adjust the valves again. I adjusted them according to comp cams instructions.

    Thanks for your help, Ed
     
  7. pomai

    pomai 1/2 ton status Premium Member

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    Thats what its doing, creating a puddle on the throttle bores.

    Thanks for your help, Ed
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    Nothing wrong with mounting the coil on the firewall, thats where mine is. :)
     
  9. vortec

    vortec 1/2 ton status

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    how much bigger are the throttle bores than on the old body? they may be big enough that the air velocity is slowed and isn't pulling the fuel downwards fast enough. are you running an aggressive cam that lowers your low-rpm vacuum? low manifold vacuum could have a similar effect. in either case, it would have to be a fairly significant difference.

    i've seen tbi setups in which the fuel pressure has been elevated well past 14 psi, bust still maintained similar spray pattern/angle to stock.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    Another thought...aren't their issues with the bored throttle bodies? I recall seeing at least a couple of places that the boring process had actually cut into the passages in the TBI.

    Even at cold startup, the injectors shouldn't be constantly wide open.
     
  11. vortec

    vortec 1/2 ton status

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    what about your fuel return line? if that plugs up it could cause some major pressure and the fuel would have nowhere to go but out the injectors. i don't know why it would be plugged up, exactly, though.
     
  12. pomai

    pomai 1/2 ton status Premium Member

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    Cam is a Comp Cam # CCA-08-302-8, Lift .480/.480, Duration 264/274, Lobe Separation 112.

    Brian from TBIchips recamended Comp Cams 08-304-8, Lift .500/.510, Duration 266/276, Lobe Separation 114. But I chickened out and went with the one size smaller cam, 08-302-8, not realizing at the time, the importance of the Lobe Separations 114 on the 304 being more computor friendly. Comp Cams said both cams would be good choices for the TBI. Got my chip from Brian.

    Throttle body bores are 2" by Xtreme-fi from ebay along with there intake manifold bored the same.

    Engine is a late model factory roller 4 blt main block. 383 rotationg assembly, scat crank & 6" rods, Probe forged pistons. World S/R torquer heads. Rear end is 14 blt, Front is a Dana 60 W/4.56 gears & 33" tires.

    Thanks for all your help, I need it. Ed
     
  13. pomai

    pomai 1/2 ton status Premium Member

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    Thats what it looks like, constantly wide open.

    Thanks for all your help, Ed
     
  14. vortec

    vortec 1/2 ton status

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    i'm looking at the cam on summitracing.com. it says it's not computer compatible. the overlap may be all wrong or something. i'm no cam expert. i know enough about them to get into trouble :wink1:.

    http://store.summitracing.com/partdetail.asp?part=CCA-CL08-302-8&autoview=sku


    i didn't see this mentioned yet; are you sure the dizzy isn't 180 degrees off? that's easy to do. really, even if it's just one tooth off, it makes a huge difference in terms of degrees.
     
  15. Thunder

    Thunder 3/4 ton status

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    I am thinking 180 degrees off also or improper timing.
    I have a bored TB and run 14 PSI no problems except a slight rich idle at 14 PSI. 13.5 is just perfict for my 350 engine.

    You are getting fuel at start up so the ECM is seeing spark pulse. Check to make sure the dist is in properly and your timing is correct.
    Have you checked for trouble codes?
     
  16. pomai

    pomai 1/2 ton status Premium Member

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    Look under part #CCA-08-302-8. Sorry I don't know how to but up a link like you did. But it is computor compatible. I checked with Comp Cams first.

    The distributor, Marker on dampner up to 0 degress on the timeing tab, then install the distributor with the rotor pointing @ # 1 on the cap. I checked to make sure the piston is a TDC. Is this correrct?

    Thanks for your help, I need it, Ed
     
  17. pomai

    pomai 1/2 ton status Premium Member

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    How big is the bore on your TB, Is it from Xtreme-fi.

    Being that I'm getting fuel at start up does that mean I am getting spark?

    Trouble codes. NO but when I try to start the enging the service engine light starts to blink untill I release the key. Brian at TBIchips said if it blinks the computor can't read the prom, he wants me to check the chip for bent pins and to see if I seated it correctly. If all is good then he wants me to send him back the chip to fix it.

    Thanks, Ed
     

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