Focus L4-2.0L DOHC VIN 5 (2003)
Compression Check: Testing and Inspection
Compression Test
General Remarks
NOTE: Removing fuses and disconnecting electrical components causes the powertrain control module (PCM) to show an error message. After
measurement has been carried out this error message should be cleared from memory by connecting scan tool.
NOTE: Only check the compression pressure with the valves set to the prescribed clearance (if this can be adjusted).
Check the compression pressure with the engine at operating temperature.
Differing designs of compressor pressure recorder and varying starter motor speeds usually only make it possible to check that the compression is the
same in all cylinders.
Check the Compression Pressure
Differing designs of compressor pressure recorder and varying starter motor speeds usually only make it possible to check that the compression is the
same in all cylinders.
Compression Test-Compression Gauge Check
1. Make sure the oil in the crankcase is of the correct viscosity and at the correct level and that the battery is correctly charged. Operate the vehicle
until the engine is at normal operating temperature. Turn the ignition switch to the OFF position, then remove all the spark plugs.
2. Set the throttle plates in the wide-open position.
3. Install a compression gauge in the No. 1 cylinder.
4. Install an auxiliary starter switch in the starting circuit. With the ignition switch in the OFF position, and using the auxiliary starter switch, crank
the engine a minimum of five compression strokes and record the highest reading. Note the approximate number of compression strokes required
to obtain the highest reading.
5. Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.
Compression Test-Test Results
The indicated compression pressures are considered within specification if the lowest reading cylinder is at least 75 percent of the highest reading.
Refer to the Compression Pressure Limit Chart.
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