Compression Pressure Check - Mitsubishi Electric Lancer Evolution-VII Workshop Manual

Crank angle sensor
connector
ENGINE - ENGINE - ENGINE -
On-vehicle Service On-vehicle Service On-vehicle Service
10. Turn the ignition switch to the "LOCK" (OFF) position
and then remove the MUT-II.

COMPRESSION PRESSURE CHECK

1. Before inspection, check that the engine oil, starter and
battery are normal. In addition, set the vehicle to the
pre-inspection condition.
2. Remove the ignition coils and spark plug cables.
3. Remove all of the spark plugs.
4. Disconnect the crank angle sensor connector.
NOTE
Doing this will prevent the engine-ECU from carrying out
ignition and fuel injection.
5. Cover the spark plug hole with a shop towel etc., and
after the engine has been cranked, check that no foreign
material is adhering to the shop towel.
Caution
(1) Keep away from the spark plug hole when
cranking.
(2) If compression is measured with water, oil, fuel,
etc., that has come from cracks inside the cylinder,
these materials will become heated and will gush
out from the spark plug hole, which is dangerous.
6. Set compression gauge to one of the spark plug holes.
7. Crank the engine with the throttle valve fully open and
measure the compression pressure.
Standard value (at engine speed of 250 r/min):
1,128 kPa
Limit (at engine speed of 250 r/min):
Min. 951 kPa
8. Measure the compression pressure for all the cylinders,
and check that the pressure differences of the cylinders are
below the limit.
Limit: Max. 98 kPa
9. If there is a cylinder with compression or a compression
difference that is outside the limit, pour a small amount
of engine oil through the spark plug hole, and repeat
the operations in steps 7 and 8.
(1) 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.
(2) 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.
10. Connect the crank angle sensor connector.
11. Install the spark plugs.
11A-11