S15/T15 4WD Jimmy L4-151 2.5L (1985)
Compression Check: Testing and Inspection
Disconnect the primary terminal from the ignition coil.
Remove all spark plugs.
Block the throttle plate wide open.
Make sure the battery is fully charged.
Starting with the compression gauge at zero, crank the engine through four compression strokes (four "puffs").
Make the compression check at each cylinder and record each reading.
If some cylinders have low compression, inject 15 ml (one table spoon, or 3 squirts from a pump type oil can) of engine oil into the combustion
chamber through the spark plug hole.
See Specifications for minimum pressure and maximum variation. See: Specifications
Normal Compression: Compression builds up quickly and evenly to specified compression on each cylinder.
Piston Rings Leaking: Compression low on first stroke, tends to build up on following strokes, but does not reach normal. Improves
considerably with addition of oil.
Valves Leaking: Low on first stroke. Does not tend to build up on following strokes. Does not improve much with addition of oil.
Head Gasket Leakage: If two adjacent cylinder have lower than normal compression, and injecting oil into cylinders does not increase the
compression, the cause may be a head gasket leak between the cylinders.