Checking Pressure Loss Of Cylinders

WARNING: Engine can turn without control (the crankshaft can turn because of the pressure in the cylinder).

Danger of crushing (injury)
Tools can become jammed (material damage)
→ The piston must be exactly at top dead center (TDC) position (secure the crankshaft).

→ Do not touch any belt drive components when building up pressure.

→ Do not insert any tools on the crankshaft belt pulley.

Adjust piston position (ignition TDC).

1.1 Screw in adapter for spark plug thread -1- by hand and connect dead center gauge -2- .

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Dead center gauge on spark plug bore (view of 991 engine)

1.2 Turn the crankshaft clockwise at the vibration damper using > 9773 - turning device until the dead center gauge indicates ignition TDC.
1.3 Remove dead center gauge.

Lock vibration damper -1- in place using > 9595/1 - locking pin-4- .

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Vibration damper
Set the pressure gauge -1- .
1. 3.1 Connect compressed air hose -2- to the pressure gauge and compressed air supply.
2. 3.2 Pull and turn the pressure-regulating valve -3- until the pointer on the pressure loss tester shows 23 % -arrow- .
3. 3.3 Find pressure-regulating valve -3- and remove compressed air hose.
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Pressure gauge

Information
- Pressure of between 6 and 12 bar is required for carrying out the pressure loss test.
- Start the test at cylinder 1 and continue according to firing order (1 - 6 - 2 - 4 - 3 - 5).
Connect pressure gauge -1- to adapter -3- .
1. 4.1 Secure the pressure gauge with a tie-wrap -2- and connect test hose to adapter -arrow- .
2. 4.2 Connect compressed air hose to the pressure gauge -1- .
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Pressure gauge (view on installed 991 engine)

Information

The pointer on the pressure gauge must be within the green area (0-25%).

If there is more than 25% pressure loss, the source of the problem must be found.
Check pressure loss.
1. 5.1 Measure pressure loss using pressure gauge.
2. 5.2 Evaluate pressure loss.
  1. 5.2.1 If pressure loss is less than 25%:
    Perform check in firing order for all other cylinders.
  2. 5.2.2 If pressure loss is greater than 25%:
    Carry out damage assessment, correct damage and carry out test in firing order for all other cylinders.