Inspection Of Compression Pressure - TOHATSU MD 70-90C2 Service Manual

2) Inspection of Compression Pressure

· To prevent accidental start of the engine,
remove lock plate (of stop switch
lanyard) from stop switch before
measuring compression pressure.
· Clean areas around spark plugs on the
cylinder before removing spark plugs to
prevent dirt from entering cylinder.
1. Start and idle engine for 5 minutes to warm up, and then
stop.
2. Shift gear into neutral (N).
3. Remove lock plate (of stop switch lanyard) from stop
switch.
Remove all spark plug caps and then all spark plugs 1.
4.
5. Install compression gauge to plug hole.
Compression Gauge:
P/N. 3AC-99030-0
6. Set free throttle lever to full open position, crank engine
until compression gauge indication stabilizes, and then
measure compression pressure.
Compression Pressure (Reference):
0.9 MPa (128 psi) [9.2 kgf/cm
Compression pressure is affected much by
cranking speed, and normally changes in the
range from 10% to 20%. Charge the battery if low.
7. If compression pressure is below specified value or varies
much among cylinders, put small amount of engine oil into
cylinders, and perform the test again.
· If compression pressure increases after the
above measure, check pistons and piston rings
for wear. Replace if necessary.
· If compression pressure does not increase,
check air injector O-ring and disc spring
condition.
· Check cylinder head gasket if the compression
pressure does not rise. Adjust or replace if
necessary.
If any of the following results is obtained by the
measurement, it is necessary to repair or replace relevant
part(s).
· The measurement is lower than specified value,
· Different between compression pressure of the cylinders
exceeds;0.105 MPa (15 psi) [1.05 kgf/cm
· The measurement is abnormally higher than specified
value.
TLDI 75/90C2 2010
CAUTION
2 ]
2 ], or
1
3
3-11