Compression, Checking

WARNING: This page is about a different car, the 2024 Audi RS 3. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Special Tools

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Special tools and workshop equipment required

Spark Plug Removal Tool:3122 B
Compression Tester Kit:V.A.G 1763
Compression Tester Kit - Adapter 5A:V.A.G 1381/5A
Fuel Injection Gauge Kit - Adapter V.A.G 1381/1:V.A.G 1381/1
Vehicle Diagnostic Tester

Procedure

Engine oil temperature at least 30 °C.
Battery voltage minimum 12.5 V.

-- Remove the noise insulation. Refer to OVERVIEW - NOISE INSULATION .

-- Disconnect the connector -arrow- for the FSI fuel injectors in the cylinder head.

Fig 2: Locating Fuel Injector Connector

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-- Remove the ignition coils. Refer to IGNITION COILS, REMOVING AND INSTALLING .

-- Remove the spark plugs with the Spark Plug Removal Tool:3122 B .

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-- Disconnect the connector -arrow- for the MPI fuel injectors.

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-- Check the compression using the Compression Tester Kit:V.A.G 1763 , Compression Tester Kit - Adapter 1:V.A.G 1381/1 and Compression Tester Kit - Adapter 5A:V.A.G 1381/5A . (Information on using the tester. Refer to the Operating Instructions).

Fig 3: Identifying Compression Tester And Adapter

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The help of a second technician is necessary for the following step.

-- Completely depress the gas pedal and operate starter long enough until the tester no longer indicates increase in pressure.

-- Repeat the procedure on each cylinder.

Compression pressure	bar pressure
New	10.0 to 14.0
Wear limit	8.0
Maximum difference between cylinders	3.0

TIP

If the test with the Compression Tester Kit:V.A.G 1763 does not lead to a clear result there are two additional tests.

In addition to the compression test a pressure test can be performed with the Pressure-Loss Tester:VAS 522 001 . The procedure for this is described in the operating instructions for the Pressure-Loss Tester :VAS 522 001 .
As an additional test the CO₂ content in the coolant expansion tank can be measured. A raised CO₂ content in the cooling system indicates a leak between the combustion chamber and the cooling system. The CO₂ content can be determined using the CO2 Coolant Tester:VAS 531 009 . The procedure for this is described in the operating instructions of the CO2 Coolant Tester :VAS 531 009 .

Assembling

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 .

-- Delete the DTC memory entries in the engine control module that have occurred during the test using the Vehicle Diagnostic Tester

Tightening Specifications

Refer to OVERVIEW - NOISE INSULATION .