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Heavy Duty Equipment Technician Red Seal Exam Prep · Question

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

Black smoke indicates incomplete combustion. This is usually caused by too much fuel for the available air (e.g., clogged air filter, faulty turbocharger) or po

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

Answer options: ✅ Unburnt fuel due to insufficient air or poor injection

  • Coolant leaking into the combustion chamber
  • Excessive oil consumption
  • A faulty fuel level sensor

Correct answer: Unburnt fuel due to insufficient air or poor injection

Explanation: Black smoke indicates incomplete combustion. This is usually caused by too much fuel for the available air (e.g., clogged air filter, faulty turbocharger) or poor fuel atomization (e.g., worn injectors).

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