What are the reasons and solutions for the generator piston knocking cylinder?

The generator piston knocking on the cylinder will cause the engine fuel consumption to be too high, oil channeling, excessive oil consumption, and poor economy. When the piston knocks the cylinder seriously, it will break the piston, and even damage the connecting rod and cylinder.

The place where the abnormal sound of piston knocking occurs is in the upper part of the engine cylinder, which generally occurs at the beginning of the piston power stroke. The piston swings or moves in the cylinder, and its head or skirt collides with the cylinder head or cylinder wall to produce abnormal noise. ‘ sound, distinct and clear. The knocking sound changes with the temperature of the engine, and the sound is more obvious under low temperature conditions; when the temperature rises, the sound weakens or disappears. When the accelerator is suddenly increased, there is a continuous metal knocking sound of “quack”. If there is a knock on the multi-cylinder, when the idle speed is increased to a high speed, the sound is noisy and disorderly.


  1. The clearance between the piston and the cylinder wall is too large.
  2. The quality of the cylinder block and ring is poor. Coupled with poor lubrication, after the engine runs for a period of time, the wear of the cylinder block and the piston is serious, which increases the gap between the piston and the cylinder block. There is an abnormal sound when hitting the cylinder.
  3. The bottom of the piston and the cylinder are severely worn, resulting in out of roundness and knocking of the cylinder.
  4. The connecting rod is bent or twisted and deformed, causing the piston to deflect incorrectly in the cylinder, resulting in abnormal wear and tearing of the piston.
  5. The piston pin and the connecting rod bushing are too tight.
  6. The piston is deformed.
  7. Poor lubrication.

Diagnosis and treatment methods

  • Open the oil filler cap, adjust the engine speed within the range with the most obvious and clear abnormal noise, and observe whether there is smoke from the oil filler port and whether blue smoke is emitted from the exhaust pipe; use a screwdriver to touch the side without the valve push rod If you touch the upper part of the cylinder, if you hit the piston, you can feel the same vibration as a small hammer hitting the concrete floor.
  • Cut off the oil one by one. If it cuts off to a certain cylinder, the sound will obviously decrease or disappear, and when the oil supply is restored, the knocking sound can be heard again, which means that the piston knocking occurs due to the excessive clearance between the cylinder and the cylinder. It should be repaired in time.
  • If you find a suspicious cylinder piston knocking, you can remove the injector of the cylinder, add a small amount of oil to the cylinder, turn the crankshaft a few times, and then put the injector back and start the engine. If the knocking sound disappears or weakens, run the engine. After a while, the knocking sound reappears, and it can be confirmed that the cylinder is knocked.
  • If the cylinder knocking sound only occurs when the engine is cold, and the sound disappears after the engine temperature is normal, you can continue to use it without repairing it, and repair it at an appropriate time.
  • If the sound of the engine is clear when the temperature is low, when the temperature rises, there is an abnormal sound at idle speed, accompanied by chattering of the body, and the higher the temperature, the louder the sound, it means that the piston is deformed or poorly lubricated, and it should be repaired in time.
  • For the knocking of the cylinder due to poor lubrication, the cause of the lubrication failure should also be found and repaired.
  • Remove the cylinder head and take out the piston for inspection. If the cylinder is found to be seriously out of round, strained, or the connecting rod is deformed, it should be replaced and repaired.
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