Compression Pressure Check
WARNING: This page is about a different variant/trim than selected.
- Before checks, check that the engine oil, starter and battery are normal. Also, set the vehicle in the following condition.
- Engine coolant temperature: 80-95°C (176-203°F)
- Lights and all accessories: OFF
- Transaxle: P range
NOTE: Vehicles for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position but this is no problem for checks. - Remove all of the ignition coils.
- Disconnect the crankshaft position sensor connector.NOTE: Doing this will prevent the engine control module from carrying out ignition and fuel injection.
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
WARNING: Keep your distance from the spark plug hole when cranking. Oil, fuel, etc., may spray out from the spark plug hole and may cause serious injury. - Cover the spark plug hole with a shop towel etc., during cranking. After the engine has been cranked, check for foreign material adhering to the shop towel.
- Set a compression gauge to one of the spark plug holes.
- Crank the engine with the throttle valve fully open and measure the compression pressure.
Standard value (at engine speed of 200 r/min):
1,560 kPa (226 psi)
Minimum limit (at engine speed of 200 r/min):
1,130 kPa (164 psi)
- Measure the compression pressure for all the cylinders, and check that the pressure difference of the cylinders are below the limit.
Limit: 98 kPa (14 psi)
- If there is a cylinder with compression or a compression difference that is outside that limit, pour a small amount of engine oil through the spark plug hole, and repeat the operations in steps 6 to 8.
- If the compression increases after oil is added, the cause of the malfunction is a worn or damaged piston ring and/or cylinder inner surface.
- If the compression does not rise after oil is added, the cause is a burnt or defective valve seat, or pressure is leaking from the gasket.
- Connect the crankshaft position sensor connector.
- Install the ignition coils.
- Use the scan tool to erase the diagnostic trouble codes.NOTE: This will erase the diagnostic trouble code resulting from the crankshaft position sensor connector being disconnected.