There are variants of compression gauges similar to the one shown in the photo…
...and also those that have a rubber tip installed instead of a spark plug instead of a threaded fitting for screwing in. Such compression gauges are simply pressed hard against the spark plug hole when checking compression.
Compression (pressure at the end of the compression stroke) in the cylinders is the most important indicator for diagnosing the condition of the engine without disassembling it. Based on its average value and the difference in values in individual cylinders, it is possible to determine with sufficient accuracy the degree of general wear of the engine cylinder-piston group parts, as well as to identify faults in this group and valve mechanism parts.
NOTE: Important conditions for correct readings when checking compression are the serviceability of the starter and its electrical circuits, as well as a fully charged battery.
NOTE: Before checking the compression in the cylinders, it is necessary to set the valve clearances correctly.
1. Start the engine and warm it up to operating temperature.
2. Remove the decorative engine cover (see Removing and installing the decorative engine cover).
3. Reduce the pressure in the engine fuel system (see Reducing pressure in the engine fuel system).
NOTE: The ECU will receive an error message when the fuel pump relay or fuse is removed or when electrical components are disconnected. This message should be cleared from the ECU RAM after performing the compression test.
4. Remove the ignition coil.
5. Unscrew and remove the spark plugs.
6. Perform the measurement according to the instructions supplied with the compression tester.
NOTE: Use a compression tester with a suitable adapter.
NOTE: Allow the starter to run with the throttle fully open until the arrow on the gauge stops moving upward.
7. Record the compression gauge readings and set its pointer to zero by pressing the air release valve.
NOTE: For compression gauges of a different design, readings may be reset in other ways (in accordance with the instructions for the device).
8. Repeat the operations for the remaining cylinders. Low compression in individual cylinders may occur as a result of loose valve seats, damaged cylinder head gaskets, broken or burnt piston rings.
Low compression in all cylinders indicates wear of the piston rings.
9. Install all parts in the reverse order of removal.
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