What are the causes of low cylinder pressure?

[VanStephen]

Causes of low cylinder pressure include: 1. Excessive side clearance or end gap of piston rings, or wear of the first sealing surface of piston rings, leading to poor sealing; 2. Excessive wear between the piston and cylinder, increasing the clearance, causing the piston to wobble during operation and affecting the proper sealing between the piston ring and cylinder; 3. Piston rings sticking or carbon buildup in the piston ring grooves, preventing the rings from exerting their elasticity and losing the first sealing surface between the compression ring and cylinder wall; 4. Cylinder scoring, which damages the sealing between the piston ring and cylinder; 5. Incorrect installation of timing gears, improper keyways, severe damage or wear of timing gears, or loosening of the camshaft timing gear profile; 6. Use of mismatched cylinder heads, such as those with different combustion chamber volumes, which can affect cylinder pressure if installed incorrectly.