Compression pressure test

Compression pressure test. The compression tester shown here with its measuring chart is a workshop tool. For home use, simpler gauge-type testers are sufficient and are also less expensive.

Measuring the compression pressure in the engine cylinders gives an indication of whether the valves and piston rings still seal well. Engine output, starting behavior, as well as oil and fuel consumption depend on this.

PROCEDURE

Drive the vehicle briefly so that the engine reaches operating temperature. Piston rings seal better when the oil is warm.

Switch off the ignition and the fuel supply. This is done differently on different models:
4-cylinder engine: disconnect the connector on the electronic ignition coil driver.

Disconnect the multi-pin connector on the central fuel injection (66 kW engine) or the connectors of all four fuel injectors (85 kW engine).

5-cylinder engine: disconnect the connector on the electronic ignition coil driver.

Remove fuse No. 17 in the fuse box.

6-cylinder engine: disconnect both connectors on the electronic ignition coil drivers.

Disconnect the connectors of all six fuel injectors. Additionally, disconnect the high-voltage lead holders on the fuel line of the third and fourth cylinders.

All models: unscrew all spark plugs.

Press the rubber cone of the pressure gauge tester firmly into the spark plug hole of the first cylinder (the sequence is not important, but it must be recorded) or onto the connecting cable leading to the spark plug connector thread.

Apply the parking brake, place the manual transmission gear selector in neutral, and place the automatic transmission selector in position 'P'.

Have an assistant crank the engine with the starter. The accelerator pedal must be fully depressed during this procedure (for better cylinder filling).

When the pressure reading stops rising, record it and proceed to the next cylinder.

Pressure values
The table below shows the compression pressure values specified by Audi: