Abnormal Noise Fault of Diesel Generator Piston Pin

The knocking sound of the piston pin in a diesel generator is a double sound (one at the top and one at the bottom of each working stroke of the piston), and the sound is relatively crisp. When idling, the noise is loud and clear. When accelerating suddenly, the noise also increases and accelerates. At high speeds, the noise is murky and unclear, and even louder when the engine is warmed up. When the diesel generator is idling or at low speed, a sharp and crisp "click" sound can be heard in the upper part of the cylinder. As the speed of the diesel generator increases, the noise increases and becomes more pronounced. In general, when the temperature of a diesel generator increases, the sound does not decrease. However, when accelerating rapidly at low speeds, the sound is very noticeable.

Cause of malfunction

1. Excessive wear on the piston pin and connecting rod bushing leads to excessive clearance and looseness.

2. The clearance between the piston pin and the pin seat hole is large.

3. The two end faces of the piston pin collide with the snap ring.

4. Poor lubrication causes severe burning of the piston pin, leading to an increase in clearance. 5. The detachment of the piston pin snap ring causes the piston pin to hit the cylinder liner and produce abnormal noise.

Diagnostic processing

1. After starting the diesel generator, run it at idle speed, and then accelerate rapidly from idle to low speed repeatedly. The sound can change with the speed. If there is a clear and continuous "click" sound during rapid acceleration, it indicates that the piston pin is ringing.

2. Stabilize the diesel engine at a speed with noticeable noise, and conduct a cylinder by cylinder shutdown test. If the noise of a certain cylinder significantly weakens or disappears after shutdown, and two consecutive noises can appear immediately or continuously at the moment of ignition, it indicates that the piston pin of the cylinder is ringing; If the noise is severe and the higher the speed, the louder the sound. If the noise does not disappear and becomes chaotic after the engine is turned off, it indicates that the clearance between the piston pin and the connecting rod small end bushing is too large. The connecting rod small end bushing or piston pin should be checked and replaced.

3. When the diesel engine is idling, there is a rhythmic and heavy "honk" sound, and the speed increases. The sound does not disappear and the engine body shakes. If a single cylinder misfire test is used, the sound becomes more pronounced, indicating that it is a piston pin movement sound. It is possible that the piston pin snap ring has fallen off and should be immediately disassembled for inspection. If it is confirmed that the snap ring has fallen off and the piston pin has scratched the cylinder wall, the cylinder liner should be replaced.

Special note: After the diesel generator experiences such abnormal noise, it is generally not allowed to idle for a long time. Before identifying the source of the abnormal noise, do not work with load to avoid causing other abnormal damage.

Dingbo Power was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to sales@dieselgeneratortech.com we will pay highly attention on your question.