1. Start the engine and make it run to normal working temperature (cooling water temperature 70 ~ 90 ℃).
2. Turn off the engine, remove the dirt around the engine spark plug and remove the spark plug.
3. Press the tapered rubber joint of the car pressure gauge into the spark plug hole of the cylinder to be tested (or screw the threaded pipe joint on the spark plug hole).
5. Use the starter to drive the crankshaft to rotate for 3 ~ 5s (not less than four compression strokes), read the reading after the pointer is stable, and then press the one-way valve to return the pointer to zero.
6. Repeat step 5. It should be noted that the number of measurements for each cylinder should not be less than two, and the measurement results should be averaged.
7. Test each cylinder in sequence as described above.
Generally, the cylinder pressure of a passenger car is greater than 900 kpa (130 PSI) and the pressure difference of each cylinder does not exceed 8% of the average of each cylinder.