Operation CHARM: Car repair manuals for everyone.

Compression Check: Testing and Inspection

CHECKING COMPRESSION PRESSURE
1. Warm up engine thoroughly. Then, stop it.
2. Remove engine cover (with power tool), air cleaner cover and battery cover.
3. Release fuel pressure.
a. Remove fuel pump fuse, and start engine. Refer to "FUEL PRESSURE RELEASE" for fuel pump fuse location.
b. After engine stalls, crank it two or three times to release all fuel pressure.
^ Let fuel pump fuse removed until the end of step 7.

4. Remove ignition coil and spark plug from each cylinder.
5. Connect engine tachometer (not required in use of CONSULT-II).





6. Install the compression gauge with adapter (SST) onto spark plug hole.
^ Use the compression gauge adapter (SST) which is required on No.7 and No.8 cylinders.





^ Use the compression gauge adapter (if no SST is used) 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.

7. 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.





Compression pressure

CAUTION: Always use a fully charged 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 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 piston rings and replace if necessary.
- If the compression pressure remains at low level despite the addition of engine oil, valves may be malfunctioning. Check valves for damage. Replace 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 cylinder head gaskets.

8. Install removed parts in the reverse order of removal.
9. Start engine, and confirm that engine runs smoothly.
10. Perform trouble diagnosis. If DTC appears, erase it. Refer to EC-72, "TROUBLE DIAGNOSIS". Introduction