Compression Test

Compression test

Special tools:
115 8540 EXTENSION 115 8540 Extension
999 9689 COMPRESSION METER 999 9689 Compression Meter

General





Warning! The ignition system works with high ignition tension and dangerous voltage in both the low and high tension circuits. There are dangerous voltages throughout the entire ignition system including the connectors.

Test the compression with the engine at operating temperature and with wide open throttle (WOT)
The normal value for B4xx4Sx is 1.3-1.5 MPa.
The normal value for B4xx4Tx is 1.1-1.3 MPa.
The maximum difference between the cylinders must not exceed 0.2 MPa.

Note! Applies to engines at operating temperature, wide open throttle (WOT) and starter motor turning at 4.2 - 5.0 r/s (250 - 300 rpm).

Disconnecting the ignition system




Remove:
- The connector from the flywheel sensor,
turbocharged engines (1) or non turbocharged engines (2)
- the engine cover.
Remove the ignition coils and spark plugs.

Note! Mark up the ignition coils before removal.

Deactivating the fuel system




Remove the cover, Then remove the system relay.

Compression test




Open the throttle completely.
Use compression meter 999 9689 COMPRESSION METER 999 9689 Compression Meter and extension socket 115 8540 EXTENSION 115 8540 Extension.
Test the compression in all the cylinders.
Install the spark plugs so that the gasket presses against the cylinder head.
Tighten to 25 Nm.
Turbocharged engines: Install the ignition coils. Tighten to 10 Nm.
Install all removed components.
Check whether any diagnostic trouble codes (DTCs) are displayed.