Important: Disconnect the crankshaft position (CKP)
sensor connector to disable the fuel and the ignition systems.
The following conditions should be considered when you check the cylinder compression:
| • | The engine should be at normal operating temperature. |
| • | The throttle must be wide open. |
| • | All of the spark plugs should be removed. |
| • | The battery must be at or near full charge. |
- Test the compression pressure for each cylinder. Low compression pressure
may be the fault of the valves or the pistons.
- Place approximately 3 squirts of oil from a plunger type oiler
into each spark plug port.
- Insert the engine compression gage into each spark plug port.
- Crank test each cylinder with 4-5 compression strokes using
the starter motor.
- The lowest reading should not be less than 70 percent of the highest
reading. The compression gage reading should not be less than 689 kPa (100 psi)
for any of the cylinders.
- Examine the gage readings obtained after the 4 puffs per cylinder
are obtained from cranking the starter motor. The readings are explained in the following
descriptions:
| • | Normal condition - Compression builds up quickly and evenly to the
specified compression on each cylinder. |
| • | Piston rings faulty - Compression is low on the 1st stroke
and tends to build up on following strokes, but the compression pressure does not
reach normal. The compression pressure improves considerably with the addition of
oil into the cylinder. |
| • | Valves faulty - Low compression pressure on the 1st stroke.
The compression pressure does not tend to build up on the following strokes. The compression
pressure does not improve much with the addition of oil onto the cylinder. |
