Start the engine and warm it up to a coolant temperature of 80–95°C.
Turn off the engine. Disconnect the high-tension spark plug wires.
Remove the spark plugs.
Rotate the engine crankshaft with the starter to remove foreign particles from the cylinders.
Fig. 2.8. Installation of the compression meter
Install the compression tester into the spark plug hole (Fig. 2.8).
Press the accelerator pedal until the throttle valve is fully open.
Turn the engine crankshaft with the starter and read the compression gauge readings.
Nominal value: 1500 kPa.
Minimum allowable value: 1400 kPa.
Repeat the measurement for all remaining cylinders and ensure that the compression difference between the cylinders is less than the maximum permissible value.
Maximum permissible value: no more than 100 kPa
If the compression in any cylinder is outside the permissible range or the difference in compression between cylinders exceeds the maximum permissible value, pour a little engine oil into the spark plug hole of that cylinder and repeat the measurements.
If the compression has increased after adding oil, the cause of the malfunction is wear or damage to the piston ring and/or cylinder bore.
If the compression does not increase after adding oil, the reasons are burnt or damaged valve seat, or gas (pressure) leakage through the cylinder head gasket.
Spark plug tightening torque: 20–30 Nm.