Compression Check: Testing and Inspection

1. Allow the engine to warm up to normal operating temperature.
2. Disconnect distributor connector.
3. Disconnect high-tension cords from spark plugs.
4. Remove spark plugs.
5. Check cylinder compression as follows:






(a) Insert a compression tester into the spark plug hole.
(b) While cranking the engine at 250 rpm or more, measure the compress pressure.

NOTE:
^ Always use a fully charged battery.
^ This measurement must be done in as short a time as possible.

(c) Repeat steps (a) and (b) for each cylinder.
Standard pressure: 1,275 kPa (13.0 kg sq/cm. 185 psi) or more.
Minimum pressure: 1,079 kPa (11.0 kg sq/cm. 156 psi).
Difference between each cylinder: 98 kPa (1.0 kg sq/cm. 14 psi) or less.
(d) If the cylinder compression in 1 or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat steps (a) and (b)for the cylinder with low compression.
- If adding oil helps the compression, it is likely that 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.
6. Install spark plugs
7. Connect high-tension cords to spark plugs
8. Connect distributor connector.