Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Compression and Cylinder Leakage Test - Diesel: Notes
For information on Ford Color Coded Illustrations refer to OEM COLOR CODING INFORMATION
- Make sure the oil in the crankcase is of the correct viscosity and at the correct level.
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NOTE: Failure to remove all fuel injectors may result in inconsistent test results.
Remove the fuel injectors.For additional information, refer to: Fuel Injectors LH . and For additional information, refer to: Fuel Injectors RH .
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NOTE: The battery charger must be left connected during the compression test and disconnected when the test is complete.
Connect a battery charger to the battery.
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NOTE: Use a fuel injector hold down from a fuel injector that has been removed for the Compression Test Adapter.
Install the Compression Tester Adapter (303-1682) and a commercially available diesel compression tester.
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NOTE: Note the approximate number of compression strokes necessary to obtain the highest reading.
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.
- Repeat the test on each cylinder, cranking the engine approximately the same number of compression strokes.
- There must not have no more than a 20% difference from the average on any given cylinder.
- Investigate and repair any cylinder(s) that are outside the 20% range.
- Remove the Compression Tester Adapter (303-1682) and the commercially available diesel compression tester.
- Disconnect the battery charger from the battery.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.