Section 96 (Engine Mechanical (SOHC)): Compression: Inspection

WARNING: This page is about a different car, the 2003 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

CAUTION: After warming-up, engine becomes very hot. Be careful not to burn yourself during measurement.

After warming-up the engine, turn the ignition switch to OFF.
Make sure that the battery is fully charged.
Lower the fuel pressure. Refer to OPERATION , Fuel.
Remove all the spark plugs.
Fully open the throttle valve.
Check the starter motor for satisfactory performance and operation.
Hold the compression gauge tight against spark plug hole.
NOTE: When using a screw-in type compression gauge, the screw (put into cylinder head spark plug hole) should be less than 18 mm (0.71 in) long.
Crank the engine by means of starter motor, and then read the maximum value on the gauge when the pointer is steady.

Fig 1: Tightening Compression Gauge Against Spark Plug
Courtesy of SUBARU OF AMERICA, INC.
Perform at least two measurements per cylinder, and make sure that the values are correct.
Compression (350 rpm and fully open throttle):
1. Standard;
  1. 1,275 kPa (13.0 kgf/cm ² , 185 psi)
2. Limit;
  1. 1,020 kPa (10.4 kgf/cm ² , 148 psi)
3. Difference between cylinders;
  1. 49 kPa (0.5 kgf/cm ² , 7 psi), or less