3126B Marine Engines Caterpillar

Use this procedure if any diagnostic codes are active for the injectors, or if you have been directed to this test from another section of this document.

Perform this procedure under conditions that are identical to the conditions that exist when the problem occurs. Typically, problems with the injector solenoid occur when the engine is warmed up and/or when the engine is under heavy loads (vibration).

These engines use Hydraulic Electronic Unit Injectors (HEUI) that are hydraulically actuated and electronically energized. The solenoid is mounted on top of the fuel injector body.

The injectors can be individually cut out to aid in troubleshooting misfire problems. Use the "Cylinder Cutout Test" on the Caterpillar Electronic Technician (Cat ET) to disable individual injectors.

The injector solenoids can also be actuated without running the engine in order to check the operation of the solenoids. Use the "Injector Solenoid Test" on Cat ET to perform this function.

Note: The "Injector Solenoid Test" will not help find leaks in the high pressure oil system.

Illustration 1	g01000968
Component locations (typical example)

Illustration 2	g01051743
Schematic

Illustration 3	g01056842
P2 ECM connector

Test Step 1. Inspect Electrical Connectors and Wiring

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the keyswitch to the OFF position. A strong electrical shock hazard is present if the keyswitch is not turned OFF.

2. Thoroughly inspect the J2/P2 Electronic Control Module (ECM) connector and the J300/P300 injector harness connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the J2/P2 ECM connector and the J300/P300 injector harness connector.

4. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

5. Check the harness and wiring for abrasion and for pinch points from the injectors to the ECM.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The wiring and the connectors appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem with the wiring and/or the connectors.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  Stop.

Test Step 2. Check for Logged Diagnostic Codes for the Injector Solenoids

1. Connect the Caterpillar Electronic Technician (Cat ET) to the service tool connector.

2. Turn the keyswitch to the ON position.

3. Monitor the "Logged Diagnostic Code" screen on Cat ET.

Expected Result:

One or more of the following diagnostic codes have been logged:

• 1-11

• 2-11

• 3-11

• 4-11

• 5-11

• 6-11

Results:

• OK - There is a logged diagnostic code for one or more of the injectors. Proceed to Test Step 4.

• Not OK - There are no logged diagnostic codes for the injectors. Proceed to Test Step 3.

Test Step 3. Check the Variation of the Injectors from Cylinder to Cylinder

1. Start the engine.

2. Allow the engine to warm up to the normal operating temperature of 77 °C (171 °F).

3. Access the "Cylinder Cutout Test" on Cat ET by accessing the following display screens in order:
   • "Diagnostics"

   • "Diagnostic Tests"

   • "Cylinder Cutout Test"

4. Enable the cooling fan, if the fan is not controlled by the ECM. If the ECM controls the cooling fan, the cooling fan will start automatically when the test begins.

5. Shut off all parasitic loads such as the air conditioning and the air compressors which could affect the results of the test.

6. Cut out each cylinder and watch the "Fuel Position" of all of the other cylinders.

7. Verify that cutting out a specific cylinder causes only a slight change to the "Fuel Position" of the other cylinders in comparison to the change to the "Fuel Position" that occurs when other cylinders are cut out. If a cylinder is cut out and only a slight change occurs to the "Fuel Position" of the other cylinders, a mechanical problem with the injector or a mechanical problem with the cylinder may exist.

8. After the test is finished, check for any new diagnostic codes that are active or logged on Cat ET.

Expected Result:

Performing the "Cylinder Cutout Test" activated a diagnostic code for one or more of the injectors.

Results:

• OK - Performing the "Cylinder Cutout Test" activated a diagnostic code for one or more of the injectors. Proceed to Test Step 4.

• Not OK - Performing the "Cylinder Cutout Test" did not activate any diagnostic codes for the injectors.

  Repair: If the engine is misfiring, or if the engine has low power, refer to Troubleshooting, "Engine Misfires, Runs Rough or Is Unstable" and Troubleshooting, "Low Power/Poor or No Response to Throttle".If a cylinder is cut out and only a slight change occurs to the "Fuel Position" of the other cylinders, there may be a mechanical problem with the injector.

  Stop.

Test Step 4. Use the Injector Solenoid Test to Test the Injector Solenoids

1. Start the engine.

2. Allow the engine to warm up to the normal operating temperature of 77 °C (171 °F).

3. Turn the keyswitch to the OFF position.

4. Turn the keyswitch to the ON position, but do not start the engine.

5. Access the "Injector Solenoid Test" by accessing the following display screens in order:
   • "Diagnostics"

   • "Diagnostic Tests"

   • "Injector Solenoid Test"

6. Activate the test.

   Note: Do not confuse the "Injector Solenoid Test" with the "Cylinder Cutout Test". The "Cylinder Cutout Test" is used to shut off fuel to a specific cylinder while the engine is running. The "Injector Solenoid Test" is used to actuate the injector solenoids. This allows the click of the injector solenoids to be heard when the engine is not running in order to determine that the circuit is functioning properly.

7. As each solenoid is energized by the ECM, an audible click can be heard at the valve cover. A black square will appear over the cylinder number when the cylinder is being fired.

8. Perform the "Injector Solenoid Test" at least two times.

Expected Result:

All cylinders indicate "OK".

Results:

• OK - There is not an electronic problem with the injectors at this time. Stop.

• Not OK "SHORT" - Cat ET displays "SHORT" for any cylinder. Proceed to Test Step 5.

• Not OK "OPEN" - Cat ET displays "OPEN" for any cylinder. Proceed to Test Step 6.

Test Step 5. Check the Wiring Harness from the ECM to the J300/P300 Injector Harness Connector for Short Circuits

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the keyswitch to the OFF position. A strong electrical shock hazard is present if the keyswitch is not turned off.

2. Disconnect the J300/P300 injector harness connector. Check for evidence of moisture entry. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Turn the keyswitch to the ON position.

4. Access the "Injector Solenoid Test" on Cat ET and begin the test.

Expected Result:

The status of the circuit for the suspect injector displays "SHORT" before the J300/P300 injector harness connector is disconnected. The status of the circuit for the suspect injector changes to "OPEN" when the J300/P300 injector harness connector is disconnected.

Results:

• OK - The status of the circuit for the suspect injector changes to "OPEN" when the J300/P300 connector is disconnected.

  Repair: Reconnect the J300/P300 connector.

  Proceed to Test Step 7.

• Not OK - The status of the circuit for the suspect injector does not change when the J300/P300 connector is disconnected. Proceed to Test Step 8.

Test Step 6. Check the Wiring Harness from the ECM to the J300/P300 Injector Harness Connector for an Open Circuit

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the keyswitch to the OFF position. A strong electrical shock hazard is present if the keyswitch is not turned off.

2. Disconnect the J300/P300 injector harness connector.

3. Insert one end of a jumper wire into the socket of the suspect injector. Insert the other end of the jumper wire into the socket of the injector common line of the J300/P300 injector harness connector.

4. Turn the keyswitch to the ON position.

5. Access the "Injector Solenoid Test" on Cat ET and begin the test.

Expected Result:

The status of the circuit for the suspect injector displays "OPEN" before the J300/P300 injector harness connector is disconnected and jumper wire is installed. The status of the circuit for the suspect injector changes to "SHORT" after the J300/P300 injector harness connector is disconnected and the jumper wire is installed.

Results:

• OK - The status of the circuit for the suspect injector changes to "SHORT" after the J300/P300 connector is disconnected and the jumper wire is installed. Reconnect the J300/P300 connector. Proceed to Test Step 9.

• Not OK - The status of the circuit for the suspect injector does not change. Proceed to Test Step 10.

Test Step 7. Check the Injector Harness for a Short Circuit between the P300 Connector and the Injector

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the keyswitch to the OFF position. A strong electrical shock hazard is present if the keyswitch is not turned OFF.

2. Remove the valve cover.

3. Disconnect the harness from the problem injector at the connector that is attached to the injector solenoid. For example, if the number one injector is the suspect injector, disconnect P301 from J301.

4. Turn the keyswitch to the ON position.

5. Access the "Injector Solenoid Test" on (Cat) ET and perform the test three times.

   Note: Ensure that the seal is installed in the harness connector before connecting the harness to the connector. If the seal is missing, use a replacement seal. Ensure that the seal is not stuck in the injector connector.

Expected Result:

The status for the injector that is disconnected indicates "OPEN" when the harness is disconnected.

Results:

• OK - The status for the injector that is disconnected changes to "OPEN" when the harness is disconnected.

  Repair: There may be a problem with the injector. Temporarily connect a new injector to the harness. Run the "Injector Solenoid Test". If all cylinders indicate "OK", turn the keyswitch to OFF and reconnect the old injector. If the original injector again reads "OPEN", replace the injector. Restore the wiring to the proper injectors. Use the "Injector Solenoid Test" to verify that the repair eliminates the problem.Do not install the valve cover until the problem is resolved. Clear all diagnostic codes.

  Stop.

• Not OK - There is a short in the wiring harness.

  Repair: Replace the wiring harness between P300 connector and the injector.Verify that the repair eliminates the problem.

  Stop.

Test Step 8. Use the "Injector Solenoid Test" to Check for Short Circuits in the ECM and in the Harness

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the keyswitch to the OFF position. A strong electrical shock hazard is present if the keyswitch is not turned OFF.

2. Disconnect the J2/P2 ECM connector and check for evidence of moisture entry. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Turn the keyswitch to the ON position.

4. Access the "Injector Solenoid Test" on Cat ET and begin the test.

   Note: When the J2/P2 ECM connector is disconnected, all of the open circuit diagnostic codes for the sensors and the open circuit diagnostic code for the air inlet heater will be active. This is normal. Clear all diagnostic codes after completing this test step.

Expected Result:

All cylinders indicate "OPEN" when the J2/P2 ECM connector is disconnected.

Results:

• OK - All cylinders indicate "OPEN". There is an open circuit in the wiring between the ECM and the J300/P300 connector.

  Repair: Repair the harness between the P2 ECM connector and the J300 injector harness connector. If the harness cannot be repaired, replace the harness.

  Stop.

• Not OK - The ECM is not responding to the open circuits at the J2/P2 ECM connector.

  Repair: Temporarily connect a test ECM. Repeat this test step. If the problem is resolved with the test ECM, install the old ECM in order to verify that the problem returns. If the test ECM works and the old ECM does not work, you may need to replace the ECM.

  Stop.

Test Step 9. Check the Injector Harness for an Open Circuit Between the P300 Connector and the Injector

Show/hide table

Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the keyswitch to the OFF position. A strong electrical shock hazard is present if the keyswitch is not turned OFF.

2. Remove the valve cover.

3. Disconnect the harness from the problem injector at the connector that is attached to the injector solenoid. For example, if the number one injector is the suspect injector, disconnect P301 from J301.

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Illustration 4	g00723455
Connector for injector solenoids

4. Insert a jumper wire across the terminals of the harness connector that was removed from the injector. For example, if the number one injector is the suspect injector, place the jumper wire across the terminals of "P301".

5. Turn the keyswitch to the ON position.

6. Access the "Injector Solenoid Test" on Cat ET and monitor the cylinder.

Expected Result:

The status of the injector with the short in place indicates an "OPEN".

Results:

• OK - There is an open circuit in the harness.

  Repair: Repair the harness between the J300 injector harness connector and the injector. Replace the harness if the harness cannot be repaired.Verify that the repair eliminates the problem.

  Stop.

• Not OK - The wiring is OK from the ECM to the injector.

  Repair: There may be a problem with the injector. Temporarily connect a new injector to the harness. Run the "Injector Solenoid Test". If all cylinders indicate "OK", turn the keyswitch to OFF and reconnect the old injector. If the original injector again reads "OPEN", replace the injector. Restore the wiring to the proper injectors. Use the "Injector Solenoid Test" to verify that the repair eliminates the problem.Do not install the valve cover until the problem is resolved. Clear all diagnostic codes.

  Stop.

Test Step 10. Use the "Injector Solenoid Test" to Check for Open Circuits in the ECM and in the Harness

Show/hide table

Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the keyswitch to the OFF position. A strong electrical shock hazard is present if the keyswitch is not turned OFF.

2. Disconnect the J2/P2 ECM connector and check for evidence of moisture entry. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Connect a 70-pin breakout T to the ECM. Do not connect the P2 engine harness connector into the breakout T.

4. Use a jumper wire to short between the socket of the suspect injector and the common socket of the suspect injector at the breakout T.

5. Turn the keyswitch to the ON position.

6. Access the "Injector Solenoid Test" on Cat ET and begin the test.

   Note: When the J2/P2 ECM connector is disconnected, all of the open circuit diagnostic codes for the sensors and the open circuit diagnostic code for the air inlet heater will be active. All of the injectors that are not jumpered will indicate an OPEN circuit during the "Injector Solenoid Test". This is normal. Clear all diagnostic codes after completing this test step.

Expected Result:

Cat ET displays "SHORT" for the cylinder with the jumper wire.

Results:

• OK - There is an open circuit in the wiring harness between the ECM and the J300 connector.

  Repair: Repair the harness between the J300 injector harness connector and the P2 ECM connector. Replace the harness if the harness cannot be repaired.Verify that the repair eliminates the problem.

  Stop.

• Not OK - The status of the circuit does not change.

  Repair: The ECM may not be responding to the short circuit. Temporarily connect a test ECM. Repeat this test step. If the problem is resolved with the test ECM, install the old ECM in order to verify that the problem returns. If the test ECM works and the old ECM does not work, you may need to replace the ECM. Refer to Troubleshooting, "Replacing the ECM".If the problem is not resolved with the test ECM the injector will need to be replaced.Verify that the repair eliminates the problem.

  Stop.