- 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 spark plugs.
- Block the throttle plate wide open.
- Charge the battery, if the battery is not fully charged.
- Start with the compression gage at 0, then crank the engine through 4 compression strokes, 4 puffs.
- Make the compression test the same for each cylinder. Record the reading.
The minimum compression in any 1 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 1 cylinder is 1 035 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 (1 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 2 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 2 cylinders. |
