The U. S. Air Force Engineering Development Program has established a method of isolating vibration from a single force function within turbojet engines. The stimulus of this program was that a large number of jet engines were removed from service for exceeding the established overall vibration. In most instances, complete overhaul of these engines did not identify the source of vibration. The result was high cost of repair in manhours and materials, plus engine unavailability. The goal of this program was to develop vibration equipment and limits that could be used in the field to isolate sources of excessive vibration and enable the using activity to remove the defective component. Techniques used to establish filtering requirements to isolate a single vibration source from the complex input, equipment specifications, and vibration limits on selected parts will be discussed. The type of instrumentation used for jet engine diagnosis using vibration trouble-shooting limit charts will be included in the discussion.