Note. Compression data for various engines are given in the chapter «Specifications for petrol and diesel engines». To carry out the test, you will need a compression tester and a simulator (adapter) spark plugs / preheater.
Measure the compression loss in each cylinder at the top meter point (the average value of the difference between the cylinders should not exceed 20%).
Note. A large loss of compression causes noise or air bubbles in the cooling system. In case of an incorrect value, the localization of the noise of leakage of air, allowing you to determine the faulty part using a technical stethoscope or rubber hose (see table «Troubleshooting» in chapter «Cylinder Leak Check»).
Examination
Attention. The control is carried out on a cold engine.
After switching off the ignition: wait 15 minutes before disconnecting the battery to ensure that the results are remembered «learning» various ECUs.
Disconnect the battery.
Disconnect the engine control unit.
Remove spark plugs or glow plugs (see corresponding operation).
Reconnect the battery.
Make sure the starter motor speed is correct (minimum speed): 2500 rpm
Install the spark plug simulator on cylinder No. 1 and tighten to 10 Nm.
Note. Use a mirror to connect the flexible hose of the compression gauge to the dummy spark plug.
Connect the compression gauge and simulator.
Connect the negative battery terminal.
Turn on the starter for 10 seconds (with the engine control unit switched off).
The pressure in the cylinder must be 20±5 bar (for new engine).
Disconnect measuring devices.
Check cylinders #2, #3 and #4 in the same way.
Note. The difference between the two cylinders must not exceed 5 bar. Hold down the pressure gauge at the end of the compression stroke.
Attention. If the compression readings are too low, check the condition of the air filter and cylinder head gasket before checking the engine for cylinder leaks.
Disconnect the battery.
Reinstall spark plugs or glow plugs (see corresponding operation).
Attach the engine control unit.
Reconnect the battery.
Perform vehicle diagnostics.