Checking Compression of Cylinders

Checking compression of cylinders

Tools





Preliminary work

1. Open the bonnet.





2. Open lid of central electrics box. To do this, loosen the four fastening screws.

WARNING Risk of electric shocks from high-voltage ignition system and danger of damage to ignition rod modules!
^ Connected ignition rod modules can be damaged.
^ Always remove the ignition rod module fuse.
^ Always disconnect ignition rod module electrical connections.

ATTENTION Risk of damage to components that affect the exhaust system!
^ Unburnt injected fuel enters the exhaust system.
^ Prevent the fuel from injecting by removing the fuse.

3. Remove fuses -7- for ignition rod modules -8- and injection system.








4. Remove spark plugs.

Tools and materials











Information

Test conditions and evaluation

Note:
^ A test document is created when a compression test is performed.
^ To prevent misuse, the information indicated by -A, B and C must be recorded.








^ The throttle must remain open during the test.
^ The vehicle voltage must remain more or less constant during the test (connect a charger).
^ The vehicle voltage must not drop below 12 V.
^ The fuses for the injection system and the ignition system must be removed during the test.
^ The engine must be at operating temperature.

Performing the test

Note: Some of the illustrations are not based on the BFD (V6) engine. They simply display the principles involved and are used to make the workflow more comprehensible.





1. Press pressure tester onto the relevant cylinder.

Note:
^ Once the starter is activated, it switches on the engine for approx. seven seconds.
^ This process should not be interrupted.
^ The vehicle voltage must not drop below 12 V during the test.
^ The throttle must always remain in the same position throughout the test. A mechanical pressing-on tool is not permitted.
^ The accelerator pedal must be fully depressed during the test.

2. Get a second person to press the starter. Testing of the cylinder is complete when the needle of the test device ceases to rise. Keep the accelerator pedal fully depressed during the test.
3. Deflate the pressure on the tester.





4. Move the scale on to another cylinder. To do this, pull the pin under the handle on the back once.
5. Then check the next cylinder according to number sequence (not according to firing order).

Subsequent work





1. Fit spark plugs.
2. Fit the ignition rod module fuses and the injection system.





3. Fit lid of central electrics box.