Compression Check: Testing and Inspection
CHECKING COMPRESSION PRESSURE1. Warm up engine thoroughly. Then, stop it.
2. Release fuel pressure.
3. Disconnect fuel pump fuse to avoid fuel injection during measurement.
4. Remove engine cover with power tool.
5. Remove ignition coil and spark plug from each cylinder.
6. Connect engine tachometer (not required in use of CONSULT-II).
7. Install compression gauge with compression gauge adapter (commercial service tool) onto spark plug hole.
^ Use compression gauge adapter whose picking up end inserted to spark plug hole is smaller than 20 mm (0.79 inch) in diameter. Otherwise, it may be caught by cylinder head during removal.
8. With accelerator pedal fully depressed, turn ignition switch to "START" for cranking. When the gauge pointer stabilizes, read the compression pressure and engine rpm. Perform these steps to check each cylinder.
CAUTION: Always use a fully changed battery to obtain specified engine speed.
^ If the engine speed is out of specified range, check battery liquid for proper gravity. Check engine speed again with normal battery gravity.
^ If compression pressure is below minimum value, check valve clearances and parts associated with combustion chamber (valve, valve seat, piston, piston ring, cylinder bore, cylinder head, cylinder head gasket). After the checking, measure compression pressure again.
^ If some cylinders have low compression pressure, pour small amount of engine oil into the spark plug hole of the cylinder to re-check it for compression.
- If the added engine oil improves the compression, the piston rings may be worn out or damaged. Check the piston rings and replace if necessary.
- If the compression pressure remains at low level despite the addition of engine oil, the valves may be malfunctioning. Check the valves for damage. Replace the valve or valve seat accordingly.
^ If two adjacent cylinders have respectively low compression pressure and their compression remains low even after the addition of engine oil, the gaskets are leaking. In such a case, replace the cylinder head gaskets.
9. After inspection is completed, install removed parts.
10. Start engine, and confirm that engine runs smoothly.
11. Perform trouble diagnosis. If DTC appears, erase it.