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| Illustration 1 | g01400491 |
Diagram of the ignition system | |
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| Illustration 2 | g00909021 |
(1) Valve cover (2) Transformer (3) Camshaft cover (4) Ignition harness | |
Each cylinder has an ignition transformer that is located under the valve cover. The master Electronic Control Module (ECM) controls ignition on the left bank and the slave ECM controls ignition on the right bank. To initiate combustion, each ECM sends a pulse of approximately 100 volts to the primary coil of each ignition transformer at the appropriate time and for the appropriate duration. The transformers increase the voltage in order to create a spark across the spark plug electrode.
Initially, the operator determines the ignition timing by using the Caterpillar Electronic Technician (ET) to program the "First Desired Timing" and "Second Desired Timing" parameters. A switch is used to select the appropriate timing. The master ECM communicates the desired timing to the slave ECM. Each ECM makes slight adjustments to the actual timing during operation.
Each ECM monitors a signal from the engine speed/timing sensor. The sensor monitors the rotation of the timing wheel which has a special tooth pattern. Through monitoring of the sensor's signal, each ECM is able to calculate the crankshaft position. This enables each ECM to properly initiate the timing of each spark.
Detonation sensors monitor the engine for detonation. The engine has ten detonation sensors. Each sensor monitors two adjacent cylinders. The sensors generate data on vibration that is processed by each ECM in order to determine detonation levels. The master ECM monitors the sensors on the left bank and the slave ECM monitors the sensors on the right bank. The slave ECM communicates the status of the right side sensors to the master ECM.
If detonation occurs, the ECM retards the ignition timing of the affected cylinder or cylinders up to six degrees. If a cylinder has been fully retarded for five seconds and the cylinder is still detonating, the ECM shuts down the engine.
Each ECM provides extensive diagnostics for the ignition system.
Ignition Transformers and Spark Plugs
Note: Ignition transformers from Electronic Ignition Systems (EIS) are not interchangeable with the transformers in this engine.
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| Illustration 3 | g01461161 |
Ignition transformer and spark plug (1) Ground spring (2) Primary connection (3) Secondary connection (4) Insulator (5) O-ring seal (6) Spark plug | |
Each transformer is grounded to a valve cover via ground spring (1). The ignition harness is connected to primary connection (2) which receives the pulse of approximately 100 volts. The output from the secondary circuit of the transformer is sent to the spark plug through secondary connection (3). The transformer's secondary circuit provides an initial 8,000 to 32,000 V to the spark plug in order to create a spark which ignites the air/fuel mixture in the cylinder.