Audi A3 Quiz
Engine

Cylinder Compression Test

In this manual: Engine
Owner's Manual — 42Routine Care and Maintenance — 32Engine — 22Engine Cooling System — 9Ventilation, Heating and Air Conditioning Systems — 11Fuel System — 9Fuel Injection System — 4Diesel engine injection system — 5Exhaust System — 9Electronic Ignition and Fuel Injection Control System — 6Charging and Starting Systems — 12Manual transmission — 12Clutch and Drive Shafts — 6Brake System — 13Front Suspension — 5Rear Suspension — 6Steering — 7Body — 70Body Electrical Equipment — 37Wiring Diagrams — 35
~2min read

GENERAL INFORMATION

Compression testing gives an indication of the engine's condition. The test results show whether the engine needs to be replaced with a new one or requires a complete overhaul. A compression tester is required to perform the test.

The pressure difference between individual cylinders must not exceed 3.0 bar. If one or more cylinders have a pressure that differs from the pressure in the other cylinders by more than 3.0 bar, this indicates a leaking cylinder head gasket, damaged valves, or wear of the piston rings or cylinder bores. If the wear limit has been reached, the engine must be repaired or replaced.

PROCEDURE

1. To perform the compression test, the engine oil temperature must be at least +30°C. The oil filter should be warm to the touch. If the temperature is below the specified value, warm up the engine. The engine must not be too hot, otherwise the threads in the cylinder head may be damaged when the spark plugs are removed.

2. Turn the ignition off.

3. Remove all spark plugs.

4. Remove the fuel pump fuse.

5. 1.6 L engines: Disconnect the injector connectors on both outer cylinders.

6. 1.6 engines: Disconnect the ignition output stage connector. The output stage is connected between the control unit and the ignition coils.

7. Crank the engine with the starter to expel carbon deposits and soot.

CAUTION

Place the manual transmission in neutral and apply the parking brake. Do not lean over the engine while cranking it. There is a risk of injury from ejected soot.

8. Screw in or press the compression tester into one of the spark plug holes.

9. Have an assistant depress the accelerator pedal and hold it in that position during the entire test.

10. Crank the engine for approximately 8 revolutions until the gauge no longer shows pressure fluctuations.

11. Check all cylinders in sequence and compare the readings with the specified value.

12. When finished, install the spark plugs.

13. Reconnect the output stage connector (1.6 L engines).

14. 1.6 L engines: Reconnect the plug connectors to the outer injectors.

CAUTION

Disconnecting plug connectors may cause fault codes to be stored in the engine control unit. It is recommended to have them erased as soon as possible at an AUDI service center.

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