Excuse me, the causes and diagnosis methods of insufficient cylinder pressure

1. Engine cylinder pressure is too low, engine power decreases, fuel or engine oil consumption increases, emissions exceed the standard, and it is difficult to start; ?

2. High cylinder pressure will lead to engine deflagration, making it difficult to start; ?

3. Uneven pressure in each cylinder of the engine will lead to unstable engine operation or lack of cylinders.

Reason: The reasons for insufficient cylinder pressure generally include serious cylinder liner wear, damaged cylinder gasket, poor contact between valve and valve seat, air leakage, too small valve clearance, mismatch between cylinder head and pressure relief device, incorrect installation of timing gear, improper installation of piston ring, etc.

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Detection:

1. The battery voltage is sufficient;

2. Preheat the engine to 80℃;

3. The oil pressure is normal

4. Remove the air filter;

5. Remove all spark plugs (fuel injectors);

6. Disconnect the fuel pump fuse or relay;

7. Disconnect the ignition high voltage line;

8. The installed pressure gauge shall not leak;

9. The throttle valve should be fully opened;

10. Turn the engine at a speed of not less than 250 rpm for 3-5 seconds.

Analysis:

Low engine cylinder pressure is usually due to poor valve sealing;

2. The cylinder depression of two adjacent cylinders of the engine is usually due to poor sealing of the cylinder gasket;

3. Open the radiator cover, bubbles can be seen during rapid acceleration, or hydrocarbons (Hc) can be detected on the radiator cover during rapid acceleration, indicating that the cylinder gasket is poorly sealed;

4. Put one end of a rubber hose next to the ear, and check the other end along the intake manifold pad, exhaust manifold pad and cylinder pad to find the leakage point quickly and accurately;

5. All cylinders of the engine are pressed down, and 20-30ml engine oil should be injected for re-inspection. The increase of cylinder pressure indicates that the cylinder, piston and piston ring are excessively worn and the piston ring is poorly sealed. Constant cylinder pressure indicates that the cylinder gasket or valve seal is poor and the air inlet is blocked;

6. The cylinder pressure of single cylinder or partial cylinder of engine is high, indicating that these cylinders are not burning well and have too much carbon deposition. 7. High cylinder pressure in all cylinders of the engine indicates poor engine exhaust.