1. Prepare the car for work (see "Preparing the car for maintenance and repair").
2. Warm up the engine to operating temperature and turn off the ignition.
3. Remove the fuse for the ECU and the engine management system circuits (see "Replacement of engine management system relays and fuses").
4. Unscrew the spark plugs (see "Spark plugs for engines 2112 and 21124 (16v) - replacement" or "Spark plugs for engines 2111 and 21114 (8v) - replacement").
5. Install the compression gauge into the spark plug hole of one of the cylinders.
Note: On an 8-valve engine, the operation looks like this:
6. Open the throttle valve fully.
7. The assistant turns on the starter for 5-10 seconds.
8. Remember or write down the device readings.
Similarly, we measure the compression in the other three cylinders. In a serviceable engine, the compression in the cylinders should be no less than 10 kgf/cm², and the difference in compression between the cylinders should be no more than 1 kgf/cm².