VALVE GP-STEERING 1668495 - Caterpillar

Ignition systems can cause electrical shocks. Avoid contacting the ignition system components and wiring.Do not attempt to remove the valve covers when the engine is operating. The transformers are grounded to the valve covers. Personal injury or death may result and the ignition system will be damaged if the valve covers are removed during engine operation. The engine will not operate without the valve covers.
Set the engine control to the OFF/RESET position. Remove the electrical power from the engine.
Remove the valve cover from the affected cylinder.
Disconnect the 2-pin connector from the ignition transformer. Visually inspect the 2-pin connector for corrosion and/or for damage.
Remove the ignition transformer from the cylinder head.
Illustration 12 g01425156
Schematic of the circuit for the ignition transformer
Measure the primary circuit by checking the voltage of the blocking diode.
Illustration 13 g01769344
Test points at the ignition transformer (partial cutaway view)
(8) Terminals for the primary circuit
(9) Screw at the ground spring
(10) Terminal for the spark plug
Set a multimeter to the diode scale. Connect the multimeter leads to the terminals (8) of the 2-pin connector. The polarity of the leads is not important. Measure the voltage between the terminals. Record the measurement.
Reverse the multimeter leads. Measure the voltage between the terminals again. Record the measurement.
Measure the resistance of the secondary circuit. Note: The resistance of the secondary coil will vary with the temperature. Illustration 14 demonstrates the relationship between the secondary coil resistance and the temperature. A reading that is within 1,000 ohms is acceptable.
Illustration 14 g01447679
Resistance versus temperature for the Ignition Transformer Gp
Set the multimeter to the 40,000 Ohm scale. Measure the resistance between screw (9) for the ground spring and terminal (10) for the spark plug . Expected Result:For the primary circuit, one of the voltage measurements is approximately 0.450 VDC. The other voltage measurement indicates an open circuit.For the secondary circuit, the resistance between the screw for the ground spring and the connector for the spark plug is within the acceptable tolerance.Results:
OK - All three of the measurements are correct.Repair: Perform the following steps:
Remove the spark plug. Check the resistance of the spark plug in order to ensure that the spark plug is in good repair. Replace any spark plugs that are out of specifications. Install the spark plug. Refer to Operation and Maintenance Manual, "Ignition System Spark Plugs - Inspect/Adjust/Replace" for details.
Switch the suspect transformer with a transformer from a different cylinder that is known to be good. Install the transformers. Install the valve covers.
Reset the control system. Start the engine. Clear any logged codes.
Operate the engine. Check for a recurrence of the problem. If the problem stays with the suspect transformer, replace the transformer.If the problem remains with the affected cylinder, the problem is in the harness or a mechanical problem is affecting the performance of the cylinder. Perform this test again or refer to Troubleshooting, "Symptom Troubleshooting" in order to troubleshoot a mechanical problem with the cylinder. Perform the necessary repairs.STOP
Not OK - At least one of the three measurements is incorrect.Repair: Replace the ignition transformer.