MIRROR AS 2594759 - Caterpillar

System Operation Description:The ignition transformers initiate combustion by providing high voltage to the spark plugs. The output from the secondary circuit of the transformer provides voltage to the terminals of the spark plug. The transformers are located underneath the valve covers. Each transformer is grounded to a valve cover via a ground spring.The secondary circuit of the transformer provides an initial 8,000 to 37,000 V to the spark plug. This voltage ionizes the air that is in the spark plug gap and generates a spark in the air gap. This voltage is then reduced to about 1,000 V. The total duration of the spark is approximately 400 microseconds.Each Electronic Control Module (ECM) can diagnose the primary circuit of the ignition transformers for open circuits and/or for short circuits. Secondary open circuits and short circuits will not directly shut down the engine. However, these conditions may lead to misfire which can cause lugging of the engine. Lugging of the engine can cause a shutdown.Note: Ignition transformers that are used with Electronic Ignition Systems (EIS) are not interchangeable with the transformers that are used with ADEM IV systems. Be sure not to interchange these components on any engine.Caterpillar spark plugs are high voltage devices with internal resistors. The spark plugs operate at a voltage that is greater than 5,000 V.Most ignition systems are affected by resistance in the secondary circuit. If a measurement of the resistance is desired, a megohmmeter must be used. A low voltage multimeter will not provide a reliable reading of the resistance. Oxidation of internal components of the spark plugs will affect the readings for those meters.Test Step 1. Use Caterpillar Electronic Technician (ET) to Check the Output of the Transformers
Remove the electrical power from the engine.
Connect Cat ET to the service tool connector.
Restore the electrical power to the engine. Set the engine control to STOP.
Set up two status screens for Cat ET. Use eight of the following labels for parameters on each Status screen:
Table 1
Parameters for the Status Screens on Cat ET
Screen 1 Screen 2
"Cylinder #1 Transformer Secondary Output Voltage Percentage" "Cylinder #2 Transformer Secondary Output Voltage Percentage"
"Cylinder #3 Transformer Secondary Output Voltage Percentage" "Cylinder #4 Transformer Secondary Output Voltage Percentage"
"Cylinder #5 Transformer Secondary Output Voltage Percentage" "Cylinder #6 Transformer Secondary Output Voltage Percentage"
"Cylinder #7 Transformer Secondary Output Voltage Percentage" "Cylinder #8 Transformer Secondary Output Voltage Percentage"
"Cylinder #9 Transformer Secondary Output Voltage Percentage" "Cylinder #10 Transformer Secondary Output Voltage Percentage"
"Cylinder #11 Transformer Secondary Output Voltage Percentage" "Cylinder #12 Transformer Secondary Output Voltage Percentage"
Start the engine. Allow the engine to warm up to normal operating temperature. Apply the normal load at rated speed.
Observe the value of the output for the secondary circuit of each transformer. Expected Result:The displayed value of the output for the secondary circuit of each transformer is between 1 and 90 percent.Results:
OK - The displayed value of the output for the secondary circuit of each transformer is between 1 and 90 percent.Repair: The ignition system components are operating properly. Investigate other possible root