Heavy Duty Equipment Technician exam: Diesel engine fundamentals

Key points

• Diesels ignite fuel by the heat of compression, not a spark.
• Black smoke usually means too much fuel or too little air.
• Blue smoke points to burning oil.
• White smoke on a cold start often means unburned fuel or coolant in the cylinder.
• Turbochargers use exhaust energy to push more air in.

Study tip

Match each smoke colour to one cause and you will get most diagnosis questions.

Try these

1. Black exhaust smoke usually means:

   1. Burning oil
   2. Too little air for the fuel
   3. Coolant leak
   4. Lean mixture
   Show answer

   B. Too little air for the fuel Rich mixture, often a restricted air intake.

2. A diesel ignites its fuel by:

   1. Spark plug
   2. Glow plug only
   3. Heat of compression
   4. Magneto
   Show answer

   C. Heat of compression Compression ignition.

3. Blue smoke points to:

   1. Burning oil
   2. Overfuelling
   3. Water in fuel
   4. Low boost
   Show answer

   A. Burning oil Oil getting past rings or seals.

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