Section 1 (Engine Mechanical (H4DO)): Compression: Inspection
WARNING: This page is about a different variant/trim than selected.
CAUTION:
After warming-up, engine becomes very hot. Be careful not to burn yourself during measurement.
NOTE:
- Compression condition of each cylinder can be confirmed as a guide before checking the compression pressure, by using the compression measurement in Subaru Select Monitor. Ref. to OPERATION , Active Test.
- In the compression measurement, the compression condition is judged by each cylinder speed. The high speed cylinder has low compression pressure and low speed cylinder has high compression pressure.
- After warming-up the engine, turn the ignition switch to OFF.
- Make sure that the battery is fully charged.
- Check the starter motor for satisfactory performance and operation.
- Remove the fuse of fuel pump from main fuse box.
- Start the engine and run it until it stalls.
- After the engine stalls, crank it for five more seconds.
- Turn the ignition switch to OFF.
- Remove all spark plugs. Ref. to REMOVAL , Spark Plug.
- Install the compression gauge to the spark plug hole.NOTE: When using a screw-in type compression gauge, the screw should be less than 25
mm (0.98 in) long. - Install the battery. Ref. to INSTALLATION , Battery.
- Turn the ignition switch to ON.
- Depress the accelerator pedal to full throttle.
- Crank the engine by starter motor and read the value when the needle of the compression gauge becomes stable.NOTE:
- Perform at least two measurements per cylinder, and make sure that the values are correct.
- If the compression pressure is out of standard, check or adjust the pistons, valves and cylinders.
Compression pressure (at 200 - 300 r/min):
Standard
1, 050 - 1, 400 kPa (11 - 14 kgf/cm 2 , 152 - 203 psi)
Difference between cylinders
100 kPa (1 kgf/cm 2 , 14 psi) or less
- After inspection, install the related parts in the reverse order of removal.