Lexus SC300 / Lexus SC400. Manual - part 558
(b) Using a 16 mm spark plug wrench, remove the eight
spark plugs.
7.
CHECK CYLINDER COMPRESSION PRESSURE
(a) Insert a compression tester into the spark plug hole.
(b) Fully open the throttle.
(c) While cranking the engine, measure the compression
pressure.
HINT: Always use a fully charged battery to obtain engine rev-
olution of 250 rpm or more.
(d) Repeat steps (a) through (c) for each cylinder.
NOTICE: This measurement must be done in as short
time as possible.
Compression pressure:
1,226 kPa (12.5 kgf/cm, 178 psi) or more
Minimum pressure:
981 kPa (10.0 kgf/cm, 142 psi)
Difference between each cylinder:
98 kPa (1.0 kgf/cm, 14 psi) or less
(e) If the cylinder compression in one or more cylinders is
low, pour a small amount of engine oil into the cylinder
through the spark plug hole and repeat steps (a) through
(c) for the cylinder with low compression.
•
If adding oil helps the compression the piston rings
and/or cylinder bore are probably worn or
damaged.
•
If pressure stays low, a valve may be sticking or
seating improper, or there may be leakage past the
gasket.
8. REINSTALL
SPARK
PLUGS
(a) Using a 16 mm plug wrench, install the eight spark
plugs.
Torque: 18 N
⋅
m (180 kgf
⋅
cm, 13 ft
⋅
lbf)
(b) Connect the eight high–tension cords to the spark
plugs.
(c) Fit the high–tension cords to the cord clamps.
(See page
–
ENGINE MECHANICAL
Compression Check
EM–31