Testing Engine Compression

Information 

• This process should not be interrupted. 
• The vehicle voltage must not drop below 12 V during the test. 
• The throttle valve 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. 
• The throttle valve must remain open during the test. 
• The vehicle voltage must remain more or less constant during the test (connect a charger). 
• The fuses for the injection system and the ignition system must be removed during the test. 
• The engine must be at operating temperature. 
• Electrical loads switched off. 
• Air conditioning switched off. 

Information 

The compression test can only issue information regarding whether the cylinder being tested is OK or not OK. Further localization of the cause of loss is achieved by a pressure loss test or a compression chamber endoscopy.

1. Connect pressure tester to the corresponding cylinder via the extensions.
   Fig 1: Checking Pressure Using Tester

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.
2. Get a second person to actuate the starter. The test for this cylinder is complete once the test equipment's pointer stops climbing. Keep the accelerator pedal fully depressed.
3. Deflate the pressure on the test equipment. Observe the operating instructions for the equipment.
4. Move the scale on to another cylinder. To do this, pull the pin once under the handle on the back.
   Fig 2: Moving Test Equipment On By One Cylinder

   Courtesy of PORSCHE CARS NORTH AMERICA, INC.
5. Then check the next cylinder according to number sequence (not according to firing order).