G3516C, G3516E, and G3512E Generator Set Engines Caterpillar

Use this procedure to troubleshoot suspect problems with the secondary circuit for the ignition transformers.

This procedure covers the following diagnostic codes:

• 401-5 Ignition Transformer Secondary #1 : Current Below Normal

• 401-6 Ignition Transformer Secondary #1 : Current Above Normal

• 402-5 Ignition Transformer Secondary #2 : Current Below Normal

• 402-6 Ignition Transformer Secondary #2 : Current Above Normal

• 403-5 Ignition Transformer Secondary #3 : Current Below Normal

• 403-6 Ignition Transformer Secondary #3 : Current Above Normal

• 404-5 Ignition Transformer Secondary #4 : Current Below Normal

• 404-6 Ignition Transformer Secondary #4 : Current Above Normal

• 405-5 Ignition Transformer Secondary #5 : Current Below Normal

• 405-6 Ignition Transformer Secondary #5 : Current Above Normal

• 406-5 Ignition Transformer Secondary #6 : Current Below Normal

• 406-6 Ignition Transformer Secondary #6 : Current Above Normal

• 407-5 Ignition Transformer Secondary #7 : Current Below Normal

• 407-6 Ignition Transformer Secondary #7 : Current Above Normal

• 408-5 Ignition Transformer Secondary #8 : Current Below Normal

• 408-6 Ignition Transformer Secondary #8 : Current Above Normal

• 409-5 Ignition Transformer Secondary #9 : Current Below Normal

• 409-6 Ignition Transformer Secondary #9 : Current Above Normal

• 410-5 Ignition Transformer Secondary #10 : Current Below Normal

• 410-6 Ignition Transformer Secondary #10 : Current Above Normal

• 411-5 Ignition Transformer Secondary #11 : Current Below Normal

• 411-6 Ignition Transformer Secondary #11 : Current Above Normal

• 412-5 Ignition Transformer Secondary #12 : Current Below Normal

• 412-6 Ignition Transformer Secondary #12 : Current Above Normal

• 413-5 Ignition Transformer Secondary #13 : Current Below Normal

• 413-6 Ignition Transformer Secondary #13 : Current Above Normal

• 414-5 Ignition Transformer Secondary #14 : Current Below Normal

• 414-6 Ignition Transformer Secondary #14 : Current Above Normal

• 415-5 Ignition Transformer Secondary #15 : Current Below Normal

• 415-6 Ignition Transformer Secondary #15 : Current Above Normal

• 416-5 Ignition Transformer Secondary #16 : Current Below Normal

• 416-6 Ignition Transformer Secondary #16 : Current Above Normal

The ignition transformers initiate combustion by providing high voltage to the spark plugs. The positive output from the secondary circuit of the transformer is at the connection for the terminal of the transformer and the terminal of the spark plug. The transformers are located underneath covers at the top of each cylinder. Each transformer is grounded to the cylinder head via a mounting flange.

Illustration 1	g01057652
Ignition transformer and spark plug (1) Mounting flange (2) 3-pin connector (3) Transformer (4) Extension (5) Secondary spark plug terminal (6) O-ring seal (7) Hole in the spark plug's precombustion chamber

The secondary circuit of the transformer provides an initial 8,000 to 37,000 volts to the spark plug. This voltage ionizes the spark plug gap. This voltage is then reduced to about 1000 volts. The total duration of the spark is approximately 400 microseconds.

The 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.

Logged diagnostic codes provide a historical record. Before you begin this procedure, use the Caterpillar Electronic Technician (ET) to print the logged codes to a file.

Note: Ignition transformers from Electronic Ignition Systems (EIS) are not interchangeable with the transformers in this engine.

Caterpillar spark plugs are high voltage devices with internal resistors. The spark plugs operate at a voltage that is greater than 5,000 volts.

Most ignition systems are not 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 because oxidation of the spark plug's internal components will affect the readings of those meters.

Test Step 1. Check the Status Screen of Cat ET for the Output of the Secondary Circuits of the Transformers

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Illustration 2	g01342726
Junction box (8) 35 amp circuit breaker

1. Set the engine control to the OFF/RESET mode. Switch 35 amp circuit breaker (1) to the OFF position.

2. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools".

3. Switch the 35 amp circuit breaker ON. Set the engine control to the STOP mode.

4. Set up two status screens for Cat ET. Use eight of the following labels for parameters on each status screen:
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   Table 1

   Parameters for the Status Screens on Cat ET
   Screen 1 Group 8	Screen 2 Group 9
   "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"
   "Cylinder #13 Transformer Secondary Output Voltage Percentage"	"Cylinder #14 Transformer Secondary Output Voltage Percentage"
   "Cylinder #15 Transformer Secondary Output Voltage Percentage"	"Cylinder #16 Transformer Secondary Output Voltage Percentage"

5. Start the engine. Apply the normal load at rated speed. Allow the engine to warm up to normal operating temperature.

6. 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. The ignition system components are operating properly.

  Repair: Investigate other possible root causes of the problem. Troubleshoot the symptom. Refer to Troubleshooting, "Troubleshooting Without A Diagnostic Code".

  STOP

• Not OK - At least one of the outputs displayed a value of 0 percent or a value that is greater than 90 percent. The ignition system components require maintenance. Proceed to Test Step 2.

Test Step 2. Inspect the Transformer

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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.

1. Set the engine control to the OFF/RESET mode. Switch the 35 amp circuit breaker OFF.
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   Illustration 3	g01342727
   Section view of the cylinders (9) Cover (3) Transformer (2) 3-pin connector

2. Remove cover (9) for the suspect cylinder.
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   NOTICE
   Pulling on the wiring harness may break the wires. Do not pull on the wiring harness.

3. Disconnect the ignition harness from 3-pin connector (2). Remove transformer (3) from the engine.
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   Illustration 4	g01342728
   Ignition transformer and spark plug (3) Transformer (4) Extension (5) Secondary terminal for the spark plug (6) O-ring seal

4. Inspect the body of transformer (3) and extension (5) for corrosion and/or for damage. Inspect the spark plug (5) for corrosion and/or for damage.

5. Inspect the connection between the transformer (3) and the extension (5) in order to ensure that the connection is not loose.

6. Inspect internal O-ring seal (6) for damage.

7. The extension has an internal terminal for the spark plug. Inspect the terminal for looseness, for corrosion, and/or for damage. Insert a spark plug into the extension and check the terminal for spring pressure.
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   NOTICE
   The extension can be scratched and damaged with a wire brush. Do not use a wire brush on the extension.

8. Clean any deposits from the inside of the extension. Use a 6V-7093 Brush with isopropyl alcohol.

Expected Result:

The transformer is in good condition.

Results:

• OK - The transformer appears to be in good condition. Proceed to Test Step 3.

• Not OK - An inspection found a problem with the transformer.

  Repair: Repair the transformer, when possible. Replace the transformer, if necessary. Be sure to use the correct transformer for the G3516C Engine.

  Reset the control system. Restart the engine. Clear the logged codes.

  STOP

Test Step 3. Check the Primary Circuit and the Secondary Circuit

1. Check the transformer and the spark plug according to the engine's Systems Operation/Testing and Adjusting Manual.

Results:

• OK - The measurements are correct. Proceed to Test Step 4.

• Not OK - At least one of the measurements is incorrect.

  Repair: Make sure that the engine control is in the OFF/RESET mode and that the 35 amp circuit breaker is OFF. Replace the ignition transformer. Make sure that you use the correct transformer for the G3516C Engine.

  Discard the spark plug. Install a new spark plug according to the instructions in the engine's Operation and Maintenance Manual.

  STOP

Test Step 4. Operate the Engine

1. Install the spark plug according to the instructions in the engine's Operation and Maintenance Manual.

2. Install the transformer and the cover.

3. Reset the control system. Clear any logged diagnostic codes.

4. Start the engine and operate the engine in order to generate the diagnostic code again.

Expected Result:

A diagnostic code is not generated.

Results:

• OK - A diagnostic code is not generated. Proceed with normal operation.

  STOP

• Not OK - A diagnostic code is generated. Proceed to Test Step 5.

Test Step 5. Isolate the Spark Plug and the Transformer

1. Switch the suspect transformer with a transformer from a different cylinder that is known to be good. Install the transformers. Install the covers.

2. Reset the control system. Clear any logged diagnostic codes.

3. Start the engine and operate the engine in order to generate the diagnostic code again.

Expected Result:

The diagnostic code is generated for the suspect transformer.

Results:

• Yes - The diagnostic code is generated for the suspect transformer.

  Repair: Make sure that the engine control is in the OFF/RESET mode and that the 35 amp circuit breaker is OFF. Replace the faulty transformer. Make sure that you use the correct transformer for the G3516C Engine. Reset the control system. Clear any logged diagnostic codes.

  STOP

• No - The diagnostic code is generated for the original cylinder.

  Repair: Make sure that the engine control is in the OFF/RESET mode and that the 35 amp circuit breaker is OFF. Install a new spark plug according to the instructions in Operation and Maintenance Manual, "Ignition System Spark Plugs - Check/Adjust/Replace". Reset the control system. Clear any logged diagnostic codes.

  STOP