Econoline E150 1/2 Ton V8-5.4L CNG VIN M (1998)
Compression Check: Testing and Inspection
Compression Test
1. Make sure the oil in the crankcase is of the correct viscosity and at the proper level and that the battery is properly 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 such as the Compression Tester 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.
