COVER 5414668 - Caterpillar

a diagnostic code is generated for the secondary circuit of the ignition transformer, the spark plug may need servicing. Misfire and a cold cylinder are other indications of a worn spark plug. Use Caterpillar Electronic Technician (ET) or the display panel, to monitor the exhaust port temperatures in order to locate a cold cylinder.The service life of the spark plugs is affected by fouling due to deposits from the oil and by peak voltages. Maintenance interval of the ignition system is also affected by voltage. Higher voltage is required by higher inlet manifold air pressures, a higher compression ratio, or retardation of the timing. Higher voltage reduces the service life of components such as spark plugs and transformers.To help predict the service life of the spark plug, use Cat ET or the display panel, to monitor the secondary voltage. The value is expressed as a percent of secondary voltage. The value increases as the spark plug gap wears over time. A new spark plug is at 20 to 30 percent. A value over 90 percent may require maintenance. A spark plug at 100 percent requires replacement. Maintaining a log of this voltage at a particular site will help to determine the proper interval for replacement of the spark plugs.For instructions on inspection and replacement of the spark plug, refer to the Operation and Maintenance Manual. For more information on the spark plug, refer to the Specifications manual for the engine.