Compression, Checking
Special tools and workshop equipment required
- Compression Tester Kit: VAG1763
- Spark Plug Socket Adapter - 3/8": VAS6919
Procedure
- Engine oil temperature at least 30 °C (86 °F).
- Battery voltage minimum 12.5 V.
-- Remove the fuse for the Fuel Pump Control Module -J538-. Refer to the appropriate Wiring Diagram.
-- Remove the ignition coils. Refer to IGNITION COILS, REMOVING AND INSTALLING .
-- Remove the spark plugs using the : VAS6919 .
With Compression Tester Kit - Adapter: VAG1763/12 :
-- Install the : VAG1763 as shown in the corresponding spark plug hole.
With : VAG1763/12A :
-- Install the : VAG1763 as shown in the corresponding spark plug hole.
Continuation:
-- Check the compression using the : VAG1763 . Refer to the Operating Manual.
- The help of a second technician is necessary for the following step.
-- Have a second technician press the accelerator pedal all the way down and operate the starter at the same time, until a pressure increase is no longer displayed on the tester.
-- Repeat the procedure on each cylinder.
| Compression Pressure | Pressure | |
|---|---|---|
| Audi A8 | Audi RS6 / RS7 / S8 | |
| New | 12.5 to 17.5 (181.3 to 284 psi) | 10.5 to 15.5 (152.3 to 225 psi) |
| Wear limit | 10.5 (152.3 psi) | 8.5 (123.3 psi) |
| Maximum difference between cylinders | 3 (43.5 psi) | 3 (43.5 psi) |
Assemble in the reverse order of removal. Note the following:
-- Install the spark plugs. Refer to OVERVIEW - IGNITION SYSTEM .
-- Install the ignition coils. Refer to IGNITION COILS, REMOVING AND INSTALLING .
-- Install the fuse for the Fuel Pump Control Module -J538-. Refer to the appropriate Wiring Diagram.
-- Delete DTC entries which were generated during testing using the Vehicle Diagnostic Tester.