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Diesel Generator Q&A: Troubleshooting Smoke, Over Speeding & Maintenance Tips

Diesel Generator Question & Answer - 1

1. Why should a DG set not be run with full fuel in the tank?

Answer: A full fuel tank creates improper pressure across fuel lines, leading to excessive black smoke emission.

2. Why is bleeding required?

Answer: The fuel system requires air bleeding under the following circumstances:

  • The engine has not been operated for a long time.

  • A fuel element has been replaced.

  • The engine was started without opening the fuel cock and has run for some time.

  • The feed pump is not functioning properly.

  • There is leakage from fuel pipes or fuel filters.

3. How to remove Air Lock?

Answer: Air lock can be removed using an air primer as per the steps below:

  • Loosen the bleeding screw of the primary fuel filter.

  • Unscrew the priming knob of the fuel pump, move it 10 to 15 times, until fuel flows out without air bubbles.

  • Tighten the air vent screw and repeat for the secondary fuel filter.

  • Finally, loosen the air vent screw of the fuel injection pump and remove air bubbles.

4. What is Thin Film Lubrication?

Answer: It is a lubrication layer between piston rings & cylinder liner, reducing metal to metal contact, friction, and wear of metal parts.

5. What is the function of a Thermostat?

Answer: The thermostat cuts the engine supply if the engine temperature increases or decreases beyond a safe level.

6. What is the function of a Thermostat Valve?

Answer:

  • At low temperature, the thermostat valve remains closed, and coolant flows through the bypass passage to the cooling pump.

  • When coolant temperature exceeds 90°C, the thermostat fully opens, closing the bypass and allowing coolant to pass through the radiator.

7. Why should the radiator cap not be opened?

Answer: The radiator cap maintains the cooling system pressure. Loosening the cap can cause pressure imbalances harmful to the DG set.

8. What is Over Speeding?

Answer: Over speeding occurs when the load is suddenly removed or there is an imbalance in the load. This causes the engine speed to increase, leading to excessive alternator speed, which can burn alternator windings.

9. What causes Black Smoke?

Answer: Improper combustion due to:

  • Choked or incorrect air cleaner.

  • Defective fuel injection system.

  • Blocked exhaust system or incorrect exhaust piping.

  • Engine overload or electrical short circuit on the load side.

10. What causes Blue Smoke?

Answer: Blue smoke occurs when oil burns in the combustion chamber, due to:

  • Excess oil in the sump.

  • Excess lubrication oil pressure.

  • Worn piston rings & liners.

  • Worn valve stems & guides.

11. What causes White Smoke?

Answer: White smoke indicates water contamination in the combustion chamber, due to:

  • Cracked cylinder head.

  • Cracked or damaged liner.

  • Water diluted diesel or damaged cylinder head gasket.

  • Water presence, which may cause hydraulic lock and severe engine damage.

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