Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
2003 Subaru Outback F6-3.0LFACTORY OEM SERVICE PROCEDURE
Compression Check: Testing and Inspection
Compression
INSPECTION
CAUTION: After warming-up, engine becomes very hot. Be careful not to burn yourself during measurement.
1. After warming-up the engine, turn ignition switch to OFF.
2. Make sure that the battery is fully charged.
3. Release fuel pressure.
4. Remove all the spark plugs.
5. Check the starter motor for satisfactory performance and operation.
6. Hold the compression gauge tight against the spark plug hole.
CAUTION: 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 inch) long.
7. Fully open throttle valve.
8. Crank the engine by means of the starter motor, and read the maximum value on the gauge when the pointer is steady.
9. Perform at least two measurements per cylinder, and make sure that the values are correct.
Compression (350 rpm and fully open throttle):
Standard; 1,275 - 1,471 kPa (13.0 - 15.0 kg/cm2, 185 - 213psi)
Limit; 1,128 kPa (11.5 kg/cm2, 164 psi)
INSPECTION
CAUTION: After warming-up, engine becomes very hot. Be careful not to burn yourself during measurement.
1. After warming-up the engine, turn ignition switch to OFF.
2. Make sure that the battery is fully charged.
3. Release fuel pressure.
4. Remove all the spark plugs.
5. Check the starter motor for satisfactory performance and operation.
6. Hold the compression gauge tight against the spark plug hole.
CAUTION: 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 inch) long.
7. Fully open throttle valve.
8. Crank the engine by means of the starter motor, and read the maximum value on the gauge when the pointer is steady.
9. Perform at least two measurements per cylinder, and make sure that the values are correct.
Compression (350 rpm and fully open throttle):
Standard; 1,275 - 1,471 kPa (13.0 - 15.0 kg/cm2, 185 - 213psi)
Limit; 1,128 kPa (11.5 kg/cm2, 164 psi)
Factory Service Tools
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.