SHAFT-DRIVE 3N8203 - Caterpillar

Detonation is engine knock that occurs after the air/fuel mixture has been ignited by the spark. The excessive mechanical stress and thermal stress can reduce the service life of the engine. There are several possible causes of detonation. Examples are a rich air/fuel mixture, overload, a high compression ratio, and high inlet manifold air temperature.Combustion of the air/fuel mixture prior to the spark is a premature ignition. This is usually caused by a hot spot in the combustion chamber. Possible sources of premature ignition are an incorrect spark plug, an incorrectly installed spark plug, and deposits in the combustion chamber. Detonation can be the result of premature ignition. The premature ignition has the effect of advanced ignition timing.Although a sensor may indicate the presence of detonation, the problem could be a premature ignition. An indication of detonation can also be caused by excessive mechanical engine noise. For these types of problems, refer to Testing and Adjusting, "Troubleshooting".
Illustration 1 g00664778
Old detonation sensor
(1) Buffer module
(2) Accelerometer
Illustration 2 g01045642
New detonation sensor
(2) Accelerometer The old detonation sensor consists of buffer module (1), detonation sensor (2), and wiring. Inspect the components. Make sure that the connectors and the wiring are in good condition.The new detonation sensor consists of an accelerometer (2). Make sure that the connectors and the wiring are in good condition.The operation of the detonation sensor can be easily tested.Use a screwdriver to tap the engine block next to the accelerometer. If the detonation increases, the sensor is operating properly.Monitor the level of detonation while you wiggle the wires for the detonation sensors at the ends of the engine harness. When possible, wiggle the wires for the detonation sensors throughout the engine harness. If the level of detonation changes, there is a problem with the wiring.If the detonation sensors generate a diagnostic code for a problem with the electrical circuit, refer to Electronic Troubleshooting, SENR6413, "G3500 Engines".