Compression Pressure Check - Mitsubishi MOTORS Space Runner 1999 Workshop Manual Supplement

Compression gauge
ENGINE <4G6-MPI> -
NOTE
Replace the three way catalyst when the CO and HC
contents are not within the standard value, even though
the result of the inspection is normal on all items.

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. Disconnect the 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 <M/T> or
engine-A/T-ECU <A/T> 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
2. If compression is measured with water, oil, fuel,
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 - 400 r/min):
Limit (at engine speed of 250 - 400 r/min):
8. Measure the compression pressure for all the cylinders,
and check that the pressure differences of the cylinders
are below the limit.
Limit: Max. 100 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
On-vehicle Service
cranking.
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.
1,400 kPa
Min. 1,060 kPa
cause of the malfunction is a worn or damaged piston
ring and/or cylinder inner surface.
11C-11