5-2
E
POWR
COMPRESSION PRESSURE MEASUREMENT
6. Measure:
• Compression pressure
Out of specification
→
Refer to steps (b)
and (c).
7. Install:
• Spark plugs
Minimum compression pressure
(reference data):
640 kPa (6.4 kgf/cm
2
, 91 psi)
Measurement steps:
a. With the throttle wide open, crank the
engine until the reading on the compres-
sion gauge stabilizes.
WARNING
To prevent sparking, ground all spark
plug leads before cranking the engine.
b. If the compression pressure is extremely
high, check the cylinder head and piston
crown for carbon deposits.
Carbon deposits
→
Eliminate.
c. If the compression pressure is below
specification and the compression pres-
sure for each cylinder is unbalanced,
squirt a few drops of oil into the cylinder
and measure the compression pressure
again.
Refer to the following table.
Compression pressure
(with oil applied to the cylinder)
Reading
Diagnosis
Higher than
without oil
Piston ring wear,
piston wear or
damage
→
Replace.
Same as without
oil
Cylinder head gas-
ket or piston possi-
bly defective
→
Replace.
T
R
.
.
Spark plug:
25 N • m (2.5 kgf • m, 18 ft • lb)