- Disconnect the ignition coil wire harness connector at the front
of the engine on the left cylinder bank and at the rear of the engine at the
right cylinder bank.
- Disconnect the fuel injector electrical harness connector at the
rear of the intake manifold.
- Remove all the spark plugs.
- Block the throttle plate wide open.
- Charge the battery if the battery is not fully charged.
- Start with the compression gauge at zero. Then crank the engine
through four compression strokes (four puffs).
- Make the compression check the same for each cylinder. Record
the reading.
The minimum compression in any one cylinder should not be less than
70 percent of the highest cylinder. No cylinder should read less than 690 kPa
(100 psi). For example, if the highest pressure in any one cylinder
is 1035 kPa (150 psi), the lowest allowable pressure for any
other cylinder would be 725 kPa (105 psi). (1035 x 70% = 725)
(150 x 70% = 105).
- If some cylinders have low compression, inject approximately 15 ml
(one tablespoon) of engine oil into the combustion chamber through the spark
plug hole.
| • | Normal -- Compression builds up quickly and evenly to the
specified compression for each cylinder. |
| • | Piston Rings Leaking -- Compression is low on the first stroke.
Then compression builds up with the following strokes but does not reach normal.
Compression improves considerably when you add oil. |
| • | Valves Leaking -- Compression is low on the first stroke.
Compression usually does not build up on the following strokes. Compression
does not improve much when you add oil. |
| • | If two adjacent cylinders have lower than normal compression,
and injecting oil into the cylinders does not increase the compression, the
cause may be a head gasket leaking between the two cylinders. |
