Diesel Generator Abnormal Noise: Diagnose Knocking & Tapping Sounds

Experienced technicians can often identify developing faults in a diesel generator set by listening carefully to its operation. Different sound patterns point to specific components. Here is a professional guide for preliminary fault location based on sound characteristics:

1. Single Knock Per Crankshaft Revolution

• Pattern: A distinct knock or tap occurring once with every full rotation (360°) of the crankshaft.

• Likely Cause: Faults in components directly connected to the crankshaft rotation.

• Components to Inspect: Pistons, piston pins, piston rings, and connecting rod bearings. Excessive wear or clearance in these parts causes the periodic impact.

2. Regular, Continuous Rhythmic Sound

• Pattern: A constant, rhythmic knocking or tapping sound synchronized with engine speed.

• Likely Cause: Issues with rotating auxiliary components.

• Components to Inspect: Timing gears, the flywheel, or a loose/damaged damper pulley. A continuous "clicking" might also indicate a failing injector.

3. Irregular, Intermittent Noise

• Pattern: A sporadic, non-rhythmic clattering, grinding, or squealing sound.

• Likely Cause: Problems with engine-mounted accessories or their drive systems.

• Components to Inspect: Alternator, starter motor (drive disengagement issues), air compressor, water pump, or cooling fan. Check for loose mounting brackets, worn bearings, or internal contact.

4. Single Knock Per Two Crankshaft Revolutions

• Pattern: A knock occurring once every two full crankshaft revolutions (720°), aligning with the camshaft speed.

• Likely Cause: Faults related to the valvetrain or camshaft drive.

• Components to Inspect: Valves, valve lifters/pushrods, valve springs, and timing gears/chain. Worn components can cause impacts at half engine speed.

5. Sharp, Metallic "Pinging" or "Clicking"

• Pattern: A clear, high-pitched metallic "ping" or rapid "click," often more audible under load.

• Likely Cause: Fuel injection issues or injector problems.

• Components to Inspect: Incorrect installation of fuel injection pump drive gear, severely worn injection pump components (like delivery valves), or faulty/leaking fuel injectors. Improper fuel grade can also cause combustion "knock."

EMEAN POWER Professional Note: This guide serves for preliminary assessment. Always shut down the generator and conduct safe, detailed inspections using proper tools to confirm the diagnosis before attempting repairs.

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