Checking Compression of Cylinders
Checking compression of cylindersTools
Preliminary work
1. Open the bonnet.
Central Electrics Box:
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.
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.
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.
Fuses For Ignition Rod Modules And Fuel Injectors:
3. Remove the fuses -7- for the ignition rod modules -8- and injection system.
Spark Plugs:
4. Remove spark plugs.
Tools and materials
Tools For Testing Pressure Loss:
Information
Evaluating test results and prerequisites for testing
Note:
^ A test document is created when a compression test is performed.
^ In order to prevent misuse, vehicle ID, date and current mileage must be entered.
Test Sheet:
^ 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.
Testing engine compression
Note: The compression test can only provide an indication as to whether the tested cylinder is working or not working properly. The cause of any loss can be further isolated by a pressure loss test.
Pressure Tester:
1. Press pressure tester onto the relevant cylinder.
Note:
^ Once the starter is activated, it switches on the engine for approximately 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. Have the starter actuated by a second person. Testing of this cylinder is complete when the needle of the test device ceases to rise. Keep the accelerator pedal fully depressed.
3. Deflate the pressure on the tester.
Moving The Test Device On By One Cylinder:
4. Move the scale on to another cylinder. To do this, pull the pin once under the handle on the back --> Moving the test device on by one cylinder.
5. Then check the next cylinder according to number sequence (not according to firing order).
Subsequent work
1. Fit spark plugs For tightening torques.
Fuses For Ignition Rod Modules And Injection Valves:
2. Fit the ignition rod module fuses and the injection system.
Central Electrics Box:
3. Fit lid of central electrics box.