Compression, Checking

Special tools and workshop equipment required 

• Spark Plug Removal Tool: 3122B 
  Fig 1: Identifying Spark Plug Removal Tool 3122B

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• Trim Removal Wedge: 3409 
  Fig 2: Identifying Trim Removal Wedge

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• Compression Tester Kit: VAG1763 
  Fig 3: Compression Tester Kit VAG 1763

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• Adapter: VAG1763/13  , not illustrated
• Engine Bung Set: VAS6122 
  Fig 4: Engine Bung Set

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Test Sequence

• Engine oil temperature at least 30 °C (86 °F).
• Battery voltage at least 12.7 V.

Preliminary work may be required depending on the model. Refer to COMPRESSION, CHECKING .

Vehicle with High-Voltage System: 

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-- Disconnect the connector -2- for the Charge Air Pressure Sensor -G31-.

-- Loosen the screw-type clamp -1- and remove the air duct pipe from the Throttle Valve Control Module -GX3- (example illustration).

-- Seal off any open lines and connections with plugs that are thoroughly cleaned from the Engine Bung Set: VAS6122  .

-- Disconnect the connection -1- for Throttle Valve Control Module -GX3-.

Fig 5: Identifying Throttle Valve Control Module Electrical Connector And Bolts

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-- Open the throttle valve by hand and lock it in open position using the Trim Removal Wedge: 3409  or a wooden wedge -arrow-.

Fig 6: Locating Throttle Valve

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-- Appropriately secure the trim removal or wooden wedge using a thread.

-- Connect the Vehicle Diagnostic Tester and switch on the ignition.

-- Select the Diagnostic  mode and start the diagnosis.

-- Select the Test plan  tab.

-- Select the Select individual test  button and select the following tree structure consecutively:

• Diagnostic-capable systems 
• 0001 - Engine electronics J623 
• 0001 - Engine electronics, functions 
• 0001 - Activate the service mode 

Continuation for All: 

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

-- Disconnect the connectors:

Fig 7: Identifying Connectors For Fuel Injectors

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1. For the FSI Fuel Injectors in the Cylinder Head
2. For MPI Fuel Injectors in the Intake Manifold, If Installed

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

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-- Install the Adapter: VAG1763/13  as shown in the respective spark plug hole and connect the Compression Tester Kit: VAG1763  .

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-- Check the compression using the Compression Tester Kit: VAG1763  . Refer to the Operating Manual.

-- Press the accelerator pedal down all the way and operate the starter long enough until the tester no longer indicates an increase in pressure.

-- Repeat the procedure on each cylinder.

TIP:

If the test with the Compression Tester Kit: VAG1763  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: VAS522001  . The procedure for this is described in the operating instructions for the Pressure-Loss Tester: VAS522001  .
• 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: VAS531009  . The procedure for this is described in the operating instructions of the CO2 Coolant Tester: VAS531009  .

Assembling 

-- 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.

There are additional procedures depending on the model. Refer to COMPRESSION, CHECKING .