Previa Van LE 4WD L4-2438cc 2.4L DOHC SC MFI (1997)
Compression Check: Testing and Inspection
NOTE: If there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.
1. Warm up and stop engine.
2. Disconnect high-tension cord from ignition coil.
3. Disconnect high-tension cords from spark plugs.
4. Remove spark plugs.
5. Check cylinder compression pressure.
(a)
Insert a compression gauge into the spark plug hole.
(b) Fully open the throttle.
(c)
While cranking the engine, measure the compression pressure.
NOTE: Always use a fully charged battery to obtain engine revolutions of 250 rpm or more.
(d) Repeat steps (a) through (c) for each cylinder.
CAUTION: This measurement must be done in as short a time as possible.
Compression pressure: 1,230 kPa (12.5 kg/cm sq., 178 psi) or more.
Minimum pressure: 880 kPa (9.0 kg/cm sq., 128 psi)
Difference between each cylinder: 98 kPa (1.0 kg/cm sq., 14 psi) or less.
(e)
If the cylinder compression in one or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole
and repeat steps (a) through (c) for cylinders with low compression.
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If adding oil helps the compression, chances are that the piston rings and/or cylinder bore are worn or damage.
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If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
6. Reinstall spark plugs.