Connect tachometer to measure engine RPM
With car running:
- Loosen injector lines at injectors one at a time.
- Observe amount of change or no change in idle speed to determine “weak” or “dead” cylinder(s).
- Idle speed should drop approximately the same on all cylinders as injector lines are loosened.
- If the problem cannot be isolated to a particular cylinder see Diagnosis II.
- If a “weak” or “dead” cylinder is found
- Check that injector line on affected cylinder is not crimped or restricted
- Check injectors
- Check valve clearance
- Check compression page
Safety
- Wear safety goggles when performing idle speed drop test.
- After perfoming idle speed drop test, be sure to wipe off all spilled fuel with rubbing alcohol. Diesel fuel spilled on hoses will cause the hoses to deteriorate.
- Keep a fire extinguisher accessible.