AR01.00-P-1200V Testing Compression Pressure

Check compression pressure
- With air cleaner on Engine side






Remove/install

DANGER:
- Risk of accident from vehicle starting off by itself when engine running. Risk of injury suffered in the form of bruises or burns to the hands when reaching in while the engine cranks or runs.
- Secure vehicle to prevent it from moving off by itself. Wear closed and close-fitting work clothes. Do not grasp hot or rotating parts.

1 Bring engine to operating temperature (approx. 80 degrees C)

NOTE: Test compression pressure only when engine is at normal operating temperature.

2 Remove air cleaner housing
- All except Model 203.065/265, 170.466:

NOTE:
- Detach the air cleaner housing from the retaining rubbers at the cylinder head covers vertically in the upward direction.
- Model 211, 220, 230.475: Unclip engine front end cover.
- Installation: Coat rubber retainers on cylinder head covers and sealing ring for hot film mass air flow sensor in air cleaner housing with lubricant.

3 Remove spark plugs.
- Remove only one spark plug per cylinder.

4 Withdraw key from electronic ignition switch EIS

NOTE: Vehicles with Keyless-Go code (889): Press start/stop button repeatedly until the ignition is switched off.

5 Crank engine with starter.

CAUTION: Do not crank engine at steering lock but use contact switch of the compression recorder.

NOTE: In order to remove the combustion residue from the cylinders, crank the engine for about 5 seconds with the starter.

6 Insert compression tester into spark plug bore.
7 Open throttle valve
- Except Model 211, 230.474/475.

8 Crank engine with starter.

CAUTION: Do not crank engine at steering lock but use contact switch of the compression recorder.

9 Carry out test procedure at the remaining cylinders in the same way.
10 Compare measurements obtained with the specified pressures
- Compression installation tolerance or new value.
- Compression pressure of service limit or limit value.
- Compression pressure of permissible difference between the individual cylinders. If the pressure is below the minimum compression pressure or if the permissible difference between individual cylinders is exceeded: Inspect cylinders for leaks.

11 Install in the reverse order.