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Black Smoke from Tail Pipe.

Discussion in 'Chevy Trucks' started by Bonanza77, Jan 1, 2004.

  1. Bonanza77

    Bonanza77 Junior Member
    Messages: 4

    :( I can't seem to get a straight answer from any of my so called mechanic experts as to why I am getting black smoke from my tail pipe. I have recently been having a problem with the engine shutting off and when I get it reved up it blows black smoke. It only happens when I hit the gas and no while I am driving. Can anyone give me some advice on what to look for. Thanks for your time in advance.

    SNOWPIMP Member
    Messages: 89

    what year and engine ??
  3. The Boss

    The Boss 2000 Club Member
    Messages: 2,099

  4. The Boss

    The Boss 2000 Club Member
    Messages: 2,099

    Hopefully ******* will see your post. He'll definatley be able to tell you what the problem is.:waving:
  5. 03GMC

    03GMC Junior Member
    from Canada
    Messages: 17

    If its a carb engine its your choke sticking,not working. Usually black smoke indicates the engine is running rich(choke).

    If its a fuelly it could be MAF,OXYGEN SENSOR,TPS, but it should have a code and check engine light will be on

    Hope that helps
  6. Bonanza77

    Bonanza77 Junior Member
    Messages: 4


    My pickup is a 1977 Chevy Bonanza with a 350, 2wd CK10 heavy 1/2, it is also a 4 barrel. Thanks for all who post and hope this clarifies.
  7. JMR

    JMR Senior Member
    Messages: 567

    From your description it sounds as though the engine is dying at stops and not when cruising. The black smoke after getting started again is from a rich fuel mixture. I would guess caused from a carb problem (stuck closed choke, bad needle and seat, stuck float) anything that might cause the engine to become flooded and die at idle.

    SNOWPIMP Member
    Messages: 89

    I agree With JMR possibly air cleaner try running it without one and see what you get!
  9. 75gmck25

    75gmck25 Senior Member
    Messages: 119

    I've never taken apart the Quadrajet on my GMC, but I've done a little work on other carburetors. Excessive richness (the black smoke) is often caused by:
    Choke is stuck or misadjusted - mixture stays rich after the engine is warm. The choke linkage might be binding on the air cleaner or other linkage, or the spring mechanism could be broken.
    Carb float has a hole in it and is sinking, or the needle in the seat is bad - the float will not shut off the flow of fuel and the truck will run very rich. It will probably run if the RPM is high enough to burn off the excess fuel.
    Temp/thermo sensor is bad - I don't know about your truck, but some have a thermo sensor that lets the carb run a little rich if the engine is cool. I've only seen these on foreign cars, but there might be something similar for GM. The sensor will be screwed into the water jacket, probably on the intake manifold.
    Power valve or accelerator pump leaking - I think the quadrajet uses a different system, but some carbs have a vacuum diaphragm and valve that gives a short shot of extra fuel in when you hit the accelerator. If it fails, the engine will bog down when you hit the accelerator, and under normal operation the valve may leak extra fuel into the carb and make it rich. This is more likely to be a problem if you have switched to a Holley carb.


  10. Dan S.

    Dan S. Member
    Messages: 31

    Check your carb linkage for a throttle stop, it is a electrical device used on some of the engines to prevent run-on when you shut off the engine. It is similar to a solenoid it holds the carb linkage in the idle position when the key is on and retracts when you shut the key off to cut off the air from the engine to stop the run-on or dieseling. If your truck has this device and it is not holding the idle position it would act like the choke is on and dump raw fuel into the engine when you let off the gas with the engine running.
    Good Luck