Compression Check - Toyota Supra 1990 Manual

EM-20
ENGINE MECHANICAL - Compression Check
EM5600
EM3002
COMPRESSION CHECK
HINT: If there is lack of power, excessive oil consump-
tion or poor fuel economy, measure the cylinder compres-
sion pressure.
(7M-GE)
1. WARM UP ENGINE
2. DISCONNECT COLD START INJECTOR CONNECTOR
3. DISCONNECT HIGH-TENSION CORD FROM IGNITION COIL
4. REMOVE THROTTLE BODY
(a) Remove the PCV hose.
(b) Disconnect the water by-pass hoses and plug the hose
end.
(c) Disconnect following hoses:
• VSV hose (for EGR)
• BVSV hose
• EGR vacuum modulator hoses
• No.7 air hose
(d) Disconnect the throttle position sensor connector.
(e) Remove the throttle body bracket.
(f) Remove the four bolts, throttle body and gasket.
5. REMOVE SPARK PLUGS
6. CHECK CYLINDER COMPRESSION PRESSURE
(a) Insert a compression gauge into the spark plug hole.
(b) While cranking the engine with the starter motor,
measure the compression pressure.
HINT: Always use a fully charged battery to obtain en-
gine speed of 250 rpm or more.
(c) Repeat steps (a) through (b) for each cylinder.
Compression pressure:
11.0 kg/cm2 (156 psi. 1,079 kPa) or more
Minimum pressure:
9.0 kg/cm2 (128 psi, 883 kPa)
Difference between each cylinder:
1.0 kg/cm2 (14 psi, 98 kPa) or less
(d) If 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 (b) for the cylinder with low compression.
• If adding oil helps the compression, chances are that
the piston rings and/or cylinder bore are worn or
damaged.
• If pressure stays low, a valve may be sticking or
seating improperly, or there may be leakage past
the gasket.