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  1. #11

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    Leaky injector could cause this, but I would also think that there would be other symptoms too. Might be worth looking into though.

    I assume there's no CEL?
    Scott

    ΜΟΛΩΝ ΛΑΒΕ

    '94 Chevy Suburban K1500
    3" exhaust w/ aero turbine non-baffled muffler
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    CB w/ 44" whip antenna


  2. #12
    Master Mechanic
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    Oct 2008
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    EGR/switch getting stuck on warm starts and functioning when in operating mode? Pindle stuck at start due to extreme carbon build up, but will not produce smoke when running. You have to hold the pedal
    down to get it to start when warm? How do your spark plugs look? Just check the easiest one and see how black it is and lets see what you get here...

    Jeff
    JMoney02

  3. #13

    Default

    One thing you might want to check is your coolant temperature sensor.

    the coolant temp sensor signal acts as a choke on fuel injected engines, when it is cold it puts more gas in the engine (like pulling the choke on your lawnmore when you first start it) and as your coolant temp warms up, it tells the computer to lean out the gas mixture.

    If the sensor is bad and is sending a cold coolant temp to computer, the computer would always be putting too much gas in. When you're starting from cold, that wouldn't be a problem, but when your engine is already warm, the air/fuel mixture would be too rich to start well and you'd need to open the throttle (pump the gas) to get more air in to allow it to start..the extra gas would come out as incomplete combustion and carbon deposits (black smoke)

    New sensor is only $11.99 and can be checked with a ohmeter

    Only thing is usually a bad CTS would cause a CEL code...but maybe it isn't bad enough to throw a code.
    Last edited by Big6ft6; 12-12-2008 at 05:02 PM.

  4. #14
    Legend

    Join Date
    Feb 2008
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    Red Wing, Minnesota, United States
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    3,356

    Default

    black smoke is usually the by-product of your engine running rich, I would be checking the intake and TBI
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
    285/75/16
    ___________________________
    Jason

  5. #15

    Default

    My first thought is fuel pressure regulator. What happens is the diaphragm between the pressurized fuel and the vacuum line ruptures, allowing excess fuel into the intake. If the leak is slow enough, you don't see a problem while it's running, but, once you shut off the engine, the fuel system "depressurizes" through the FPR into the intake. Once you get enough in the intake, it will act "flooded" when you try to start it. If you wait long enough, the excess fuel in the intake will dissipate and you don't have a problem.

    Easy enough to check: simply pull the vacuum line off of the FPR (As I understand it, your 7.4 FPR is easy enough to get to) after the engine's been running and see if there's any gasoline in the vacuum line. If yes, then replace FPR.

    If no, I'd probably put a fuel pressure gauge on it and see if the fuel system holds pressure.
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

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