Compression Test - Compression Gauge Check: Notes
WARNING: This page is about a different car, the 2012 Ford Pickup, 2012 Ford F550 Super Duty, and 2012 Ford F450 Super Duty. However, it is still accessible from the selected car via links, so may be relevant.
- 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.
- Set the throttle plates in the wide-open position.
- Install a compression gauge in the No. 1 cylinder.
- 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 5 compression strokes and record the highest reading. Note the approximate number of compression strokes required to obtain the highest reading.
- 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% of the highest reading. Refer to the Compression Pressure Limit Chart.
Compression Pressure Limit Chart
If one or more cylinders reads low, squirt approximately one tablespoon of engine oil on top of the pistons in the low-reading cylinders. Repeat the compression pressure check on these cylinders.