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Heavy Duty Equipment Technician Red Seal Exam Prep · Question

A diesel engine is producing black smoke from the exhaust. What is the most likely cause?

Black smoke typically indicates unburnt fuel particles, which result from incomplete combustion. This can be caused by too much fuel, not enough air, or incorre

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Question: A diesel engine is producing black smoke from the exhaust. What is the most likely cause?

Answer options:

  • Lean fuel mixture
  • Excessive engine oil consumption ✅ Incomplete combustion due to insufficient air or overfuelling
  • Coolant leak into the combustion chamber

Correct answer: Incomplete combustion due to insufficient air or overfuelling

Explanation: Black smoke typically indicates unburnt fuel particles, which result from incomplete combustion. This can be caused by too much fuel, not enough air, or incorrect injection timing.

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