Lexus SC300 / Lexus SC400. Service manual — part 426
COMPRESSION CHECK
HINT: If there is lack of power, excessive oil consumption or
poor fuel economy, measure the compression pressure.
1.
WARM UP AND STOP ENGINE
Allow the engine to warm up to normal operating tempera-
ture.
2.
REMOVE NO.3 TIMING BELT COVERS
(See steps 1, 5 to 10 and 14 on pages
3.
DISCONNECT COLD START INJECTOR CONNECTOR
4. DISCONNECT RH CAM POSITION SENSOR
CONNECTOR
(a) Disconnect the connector from the ignition coil bracket.
(b) Disconnect the sensor connector.
5. DISCONNECT LH CAM POSITION SENSOR
CONNECTOR
6. REMOVE
SPARK
PLUGS
(a) Disconnect the eight high–tension cords from the spark
plugs.
Disconnect the high–tension cords at rubber boot. Do
not pull on the cords.
NOTICE: Pulling on or bending the cords may damage
the conductor inside.
EM–30
–
ENGINE MECHANICAL
Compression Check
(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
9. RECONNECT
RH
CAM POSITION SENSOR CONNECTOR
(a) Connect the sensor connector.
(b) Connect the connector to the ignition coil bracket.
10. RECONNECT
LH
CAM POSITION SENSOR CONNECTOR
11. RECONNECT COLD START INJECTOR CONNECTOR
12. REINSTALL NO.3 TIMING BELT COVERS
(See steps 28 to 30, 34 to 37, 40 and 41 on pages
to 27)
EM–32
–
ENGINE MECHANICAL
Compression Check
TIMING BELT
COMPONENTS FOR REMOVAL AND
INSTALLATION
–
ENGINE MECHANICAL
Timing Belt
EM–33
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