The maximum permissible pressure difference in individual cylinders may be 2.0 bar. If one or more cylinders have a pressure difference greater than 2.0 bar compared to others, this indicates defective valves, worn piston rings or cylinder running surfaces. If the wear limit is reached, the engine must be repaired or replaced.
| Engine type and displacement | Compression pressure, bar |
| 4-cyl. petrol | 11-13 |
| 2.4 l; V6 2.9 l | 12,4-14,1 |
| V6 2.8 l | 11,5-12,5 |
| diesel | 20-25 |
The data in the table are approximate. Due to the different starter speeds and different designs of compression gauges, it is not always possible to determine the actual compression pressure. Therefore, in most cases, comparative measurements are made between individual cylinders.
The compression test should be performed on a warm engine. The engine oil temperature should be at least +30°C. The oil filter should be noticeably warm to the touch, otherwise the engine should be warmed up while the car is moving. The engine temperature should not be too high, otherwise the thread in the cylinder head may be damaged when the spark plugs are unscrewed.
Turn off the ignition.
Petrol engine: Disconnect the plug connector of terminal 15 at the ignition coil.
Engine with catalytic converter: remove the fuel pump electrical circuit fuse, see p. 156.
Diesel engine
Disconnect the "arrow" plug connector of the fuel supply switch at the high-pressure fuel pump.
Note: If this is not done, when the starter is turned on, diesel fuel will be injected into the combustion chambers by the injectors.
Disconnect the multi-pin plug connector of the preheating system relay "arrow".
Petrol engine: remove the spark plug caps from all spark plugs. A special clamp, such as HAZET 1849, is used for this purpose.
Finally, blow out the spark plug recesses in the cylinder head with compressed air and unscrew the spark plugs with a suitable wrench.
Diesel engine: remove glow plugs, see p. 76.
Turn the engine crankshaft with the starter to throw out carbon deposits and soot through the holes in the cylinder head.
Attention! Shift the gearbox to neutral and apply the handbrake.
Press the compression gauge against the spark plug/glow plug hole or screw it into the hole in accordance with the service manual.
The assistant must fully depress the accelerator pedal and hold it with his foot throughout the entire test.
Turn the engine crankshaft with the starter approximately 8 revolutions until the readings on the instrument scale stop changing.
Check all cylinders in sequence and compare the results obtained with the prescribed pressure values.
Gasoline engine
After this, screw in the spark plugs and connect the high-voltage wires, see p. 51.
Connect the plug connector to the ignition coil.
Diesel engine
Install glow plugs, see p. 76.
Connect the multi-pin plug connector of the preheating system relay.
Connect the plug connector of the fuel supply switch at the fuel pump.
Engine with catalytic converter: Reinstall the fuel pump electrical circuit fuse.