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adreeza 10/3/2011
1980 Mercedes Benz 450SL Base 8 Cyl 4.5L - Engine
My Benz has been backfiring black smoke every 6 months or so and is running rough. Does anyone have any idea why?
This is actually a 1973 450sl Mercedes not a 1980 .
1 Answer
  • Spoon Sports
    Spoon Sports 10/3/2011
    Black smoke is caused by excess fuel that has entered the cylinder area and cannot be burned completely. Another term for excess fuel is "running rich." Poor fuel mileage is also a common complaint when black smoke comes out of the tailpipe. Black smoke out the tailpipe is the least cause for alarm. Excess fuel will usually effect engine performance, reduce fuel economy, and produce a fuel odor.

    How did the fuel get into the cylinder in the first place? Some of the causes of excess fuel are a carburetor that is out of adjustment, a faulty fuel pump, a leaky fuel injector, or a faulty engine computer or computer sensor. If black smoke is present, check the engine oil as in the white smoke example to make sure excess fuel has not contaminated it. Do not start the engine if a heavy, raw fuel smell can be detected in the engine oil. Call your mechanic and advise him of what you have found.

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