For the measurement of cylinder compression pressure, it is mainly the pressure at the end of compression of a four-stroke engine. Due to the pressure of the cylinder, the viscosity of the oil and the coordination of the cylinder-piston group, whether the adjustment of the valve train is correct, the sealing performance of the cylinder gasket and other factors, when measuring the pressure of the engine cylinder, the cylinder-piston group can be diagnosed. If the sealing performance of the piston ring, valve and cylinder gasket is good, the clearance of the valve must be appropriate.

The main method of testing the tightness of the engine is to first use compressed air to clean the dirt around the spark plug, and then remove the spark plug. For gasoline, the secondary high-voltage line of the ignition system should be pulled out to reliably ground the iron. , This is to prevent the phenomenon of electric shock and fire, insert the conical rubber plug of the special cylinder pressure gauge into the spark plug hole measured by the cylinder, and it must be straightened and pressed tightly. For the special throttle valve, it must be placed in full In the open position, the starter must drive the corresponding crankshaft to rotate. If the pointer of the pressure gauge has a certain hold, it must stop rotating after the worst pressure reading. Finally, remove the pressure gauge and record the reading.