Compression Check: Testing and Inspection

Compression Check
If there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.

Procedure
1. Allow the engine to warm up to normal operating temperature.
2. Remove spark plugs.
3. Check cylinder compression pressure.
(a) Insert a compression gauge into the spark plug hole.
(b) Fully open the throttle.
(c) While cranking the engine, measure the compression pressure.

NOTE:
^ Always use a fully charged battery to obtain engine speed of 250 rpm or more.
^ Measurement of all cylinders must be done in as short a time as possible.

(d) Repeat steps (a) through (c) for each cylinder.

Compression pressure:
Standard value: 1226 kPa (12.5 kg/sq cm, 178 psi) or more
Minimum pressure: 981 kPa (10.0 kg/sq cm, 142 psi)
Difference between each cylinder: 98 kPa (1.0 kg/sq cm, 14 psi) or less

NOTE:
^ 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 cylinders with low compression.
^ If adding oil helps the compression, chances are that the piston rings and/or cylinder bore are worn or damage.
^ If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.

4. Reinstall spark plugs.