3126B Petroleum Engine Injector Solenoid Circuit - Test Caterpillar


Injector Solenoid Circuit - Test
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System Operation Description:

Use this procedure for the following conditions:

  • An injector solenoid may have a problem.

  • You have been directed to this procedure from Troubleshooting, "Troubleshooting without a Diagnostic Code".

  • There is an active diagnostic code for an injector solenoid.

Use this procedure for the following diagnostic codes:

  • 1-11 Injector Cylinder #1 fault

  • 2-11 Injector Cylinder #2 fault

  • 3-11 Injector Cylinder #3 fault

  • 4-11 Injector Cylinder #4 fault

  • 5-11 Injector Cylinder #5 fault

  • 6-11 Injector Cylinder #6 fault

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 vibration (heavy loads).

These engines have Electronic Unit Injectors (EUI) that are hydraulically actuated and electronically controlled. The Engine Control Module (ECM) sends a 105 volt pulse to each injector solenoid. The pulse is sent at the proper time and at the correct duration for a given engine load and speed. The solenoid is mounted on top of the fuel injector body.

If an open is detected in the solenoid circuit, a diagnostic code is generated. The ECM continues to try to fire the injector. If a short is detected, a diagnostic code is generated. The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.

The AVSpare Electronic Technician (ET) includes the following tests that aid in troubleshooting the injector solenoids:

"Cylinder Cutout Test"

All active diagnostic codes must be repaired before running the "Cylinder Cutout Test". Use the "Cylinder Cutout Test" to diagnose a malfunctioning injector while the engine is running. When a good injector is cut out, the "Fuel Position" should change. The change in the fuel position is caused by the other injectors that are compensating for the cut out injector. If a malfunctioning injector is cut out, the "Fuel Position" will not change. The "Cylinder Cutout Test" is used to isolate the malfunctioning injector in order to avoid replacement of good injectors.

"Injector Solenoid Test"

Use the "Injector Solenoid Test" to aid in diagnosing an open circuit or a short circuit while the engine is not running. The "Injector Solenoid Test" briefly activates each solenoid. A good solenoid will create an audible click when the solenoid is activated. Cat ET will indicate the status of the solenoid as "OK", "Open", or "Short".

Note: Refer to Illustration 1. Two injector solenoids share a common supply wire. For this reason, an open circuit or a short circuit in a supply wire could cause diagnostic codes for two injector solenoids.




Illustration 1g01129644

Schematic for the injector solenoids

------ WARNING! ------

The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.

----------------------

Test Step 1. Inspect the Electrical Connectors and the Wiring

    ------ WARNING! ------

    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.



    Illustration 2g01129744

    Left side view

    (1) J300/P300 Injector harness connector

    (2) J2/P2 ECM connector

  1. Thoroughly inspect connectors (1) and (2). Refer to Troubleshooting, "Electrical Connectors - Inspect".



    Illustration 3g01129751

    P2 terminals that are associated with the injector solenoids

    (P2-36) Injector 1 return

    (P2-37) Injector 2 return

    (P2-38) Injector 3 return

    (P2-39) Injector 4 return

    (P2-44) Injector 1 & 2 supply

    (P2-45) Injector 3 & 4 supply

    (P2-56) Injector 5 & 6 supply

    (P2-54) Injector 5 return

    (P2-55) Injector 6 return




    Illustration 4g01129758

    P300 terminals that are associated with the injector solenoids

    (P300-1) Injector 1 supply

    (P300-2) Injector 2 supply

    (P300-3) Injector 3 supply

    (P300-4) Injector 4 supply

    (P300-5) Injector 5 supply

    (P300-6) Injector 6 supply

    (P300-7) Injector 6 return

    (P300-8) Injector 5 return

    (P300-9) Injector 4 return

    (P300-10) Injector 3 return

    (P300-11) Injector 2 return

    (P300-12) Injector 1 return

  1. Perform a 45 N (10 lb) pull test on each of the wires that are associated with injector solenoids.

  1. Check the allen head screw on the ECM connectors for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque value.

  1. Check the harness and the wiring for abrasion and for pinch points from the P300 connector 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, or of pinch points.

Results:

  • OK - The harness and wiring are okay. Proceed to Test Step 2.

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

    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 the Variation of the Injectors between Cylinders

  1. Start the engine.

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

  1. Access the "Cylinder Cutout Test" by accessing the following display screens:

    • "Diagnostics"

    • "Diagnostic Tests"

    • "Cylinder Cutout Test"

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

  1. Set the engine speed to 1000 ± 20 rpm.

  1. Select the start button at the bottom of the screen for the cylinder cutout test on Cat ET.

  1. Select the "4 Cylinder Cutout Test" which is the default test.

  1. Follow the instructions that are provided by Cat ET in order to complete the cylinder cutout test. The cylinder cutout test is interactive so the procedure is guided to the finish. The test results are displayed on Cat ET.

    The "4 Cylinder Cutout Test" will not run unless certain conditions are present. For example, Cat ET will not allow the "4 Cylinder Cutout Test" to occur when the temperature of the engine coolant is too low. In this case, warm the engine or perform the test manually.

  1. You may manually cut out a cylinder, if necessary. Highlight a cylinder and select the "Change" button at the bottom of the screen. The injector for that cylinder will be disabled. Check for a difference in the sound, feel, or power of the engine. Also, look for a change to the operating parameters that are displayed on the "Cylinder Cutout Test" screen.

Expected Result:

The cylinder cutout test indicates that all of the injectors are operating correctly.

Results:

  • OK - The cylinder cutout test indicates that all of the injectors are operating correctly.

    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".

    STOP

  • Not OK - The cylinder cutout test indicates that at least one of the injectors is not operating correctly. Proceed to Test Step 3.

Test Step 3. Test the Injector Solenoids

  1. Start the engine.

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

  1. Stop the engine.

  1. Turn the keyswitch to the ON position.

  1. Access the "Injector Solenoid Test" by accessing the following display screens:

    • "Diagnostics"

    • "Diagnostic Tests"

    • "Injector Solenoid Test"

  1. Activate the "Injector Solenoid Test".

  1. As each solenoid is energized by the ECM, an audible click can be heard at the valve cover.

  1. Allow the "Injector Solenoid Test" to continue until each cylinder is activated at least two times.

Expected Result:

All cylinders indicate "OK" on Cat ET.

Results:

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

    Repair: The problem appears to be resolved. The problem was probably caused by a poor electrical connection in a connector.If the codes continue to be logged, refer to Troubleshooting, "Electrical Connectors - Inspect".If the engine is misfiring or if the engine has low power, refer to Troubleshooting, "Engine Misfires, Runs Rough or Is Unstable" or Troubleshooting, "Low Power/Poor or No Response to Throttle".

    STOP

  • Not OK - Open - Note the cylinder that indicates "Open". Proceed to Test Step 4.

  • Not OK - Short - Note the cylinder that indicates "Short". Proceed to Test Step 7.

Test Step 4. Check the Harness between the ECM and the Valve Cover Base for an Open Circuit

    ------ WARNING! ------

    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.

  1. Disconnect the P300 injector harness connector.

  1. Turn the keyswitch to the ON position.

  1. Fabricate a jumper wire 100 mm (4 inch) long with Deutsch pins on both ends of the wire.

  1. Insert one end of the jumper wire into the P300 socket for the suspect injector's supply wire. Insert the other end of the jumper wire into the P300 socket for the suspect injector's return wire. This will replace the injector solenoid with a short circuit.

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

  1. Repeat this test for each suspect injector. Stop the "Injector Solenoid Test" before handling the jumper wire.

Expected Result:

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

Results:

  • OK - Cat ET displays "Open" for the cylinder with the jumper wire. There is a problem in the wiring between the ECM and the P300 connector. Proceed to Test Step 6.

  • Not OK - Cat ET displays "Short" for the cylinder with the jumper wire. The harness between the ECM and the P300 connector does not have an open circuit. Proceed to Test Step 5.

Test Step 5. Check the Injector Harness under the Valve Cover for an Open Circuit

    ------ WARNING! ------

    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.

  1. Remove the valve cover.

  1. Disconnect the harness connector from the suspect injector.

  1. Thoroughly clean the terminals on the injector solenoid and the harness connector.

  1. Insert the ends of a jumper wire into each socket in the harness connector for the suspect injector. This will replace the injector solenoid with a short circuit.

  1. Turn the keyswitch to the ON position.

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

Expected Result:

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

Results:

  • OK - Cat ET displays "Open" for the cylinder with the jumper wire. There is a problem with the injector harness under the valve cover. There may be a problem with a connector.

    Repair: Repair the wiring and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

  • Not OK - Cat ET displays "Short" for the cylinder with the jumper wire. The wiring is okay.

    Repair: Replace the faulty injector. Verify that the problem is resolved.

    STOP

Test Step 6. Check the ECM for Proper Operation

    ------ WARNING! ------

    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.

    Note: When the P2 ECM connector is disconnected, numerous diagnostic codes will be generated when the keyswitch is turned to the ON position. This is normal. Ignore the codes and clear the codes after you complete this Test Step.

  1. Disconnect the P2 connector.

  1. Use a jumper wire in order to create a short circuit on J2 between the terminals for the suspect injector's supply and suspect injector's return.

  1. Turn the keyswitch to the ON position.

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

Expected Result:

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

Results:

  • OK - Cat ET displays "Short" for the cylinder with the jumper wire. The ECM detected the short circuit.

    Repair: If two injector solenoids that share a supply wire indicated "Open" from the previous step, the open circuit is probably caused by an open in the supply wire. There may be a problem in a connector.Repair the wiring and/or the connector. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

  • Not OK - Cat ET did not display "Short" for the cylinder with the jumper wire. The ECM did not detect the short circuit.

    Repair: Perform the following procedure:

    1. Temporarily connect a test ECM. Refer to Troubleshooting, "Replacing the ECM".

    1. Perform the "Injector Solenoid Test".

      If the test ECM fixes the problem, connect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.

    STOP

Test Step 7. Check the Harness between the ECM and the Valve Cover Base for a Short Circuit

    ------ WARNING! ------

    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.

  1. Disconnect the P300 connector.

  1. Turn the keyswitch to the ON position.

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

Expected Result:

All cylinders indicate "Open" on Cat ET.

Results:

  • OK - All cylinders indicate "Open" on Cat ET. Proceed to Test Step 9.

  • Not OK - One or more cylinders indicate "Short" on Cat ET. Note the cylinders that indicate "Short". Proceed to Test Step 8.

Test Step 8. Check the ECM for Proper Operation

    ------ WARNING! ------

    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.

    Note: When the P2 ECM connector is disconnected, numerous diagnostic codes will be generated when the keyswitch is turned to the ON position. This is normal. Ignore the codes and clear the codes after you complete this Test Step.

  1. Disconnect the P2 ECM connector.

  1. Turn the keyswitch to the ON position.

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

Expected Result:

All injector solenoids indicate "Open" when the P2 connector is disconnected.

Results:

  • OK - All injector solenoids indicate "Open" when the P2 connector is disconnected. There is a short circuit in the engine harness. There may be a problem with a connector.

    Repair: Inspect the connectors for moisture and for corrosion. Repair the wiring and/or the connector, when possible. Replace parts, if necessary. Clear all diagnostic codes after you complete this test step. Verify that the problem is resolved.

    STOP

  • Not OK - At least one injector solenoid does not indicate "Open". There is a problem with the ECM.

    Repair: Perform the following procedure:

    1. Temporarily connect a test ECM. Refer to Troubleshooting, "Replacing the ECM".

    1. Perform the "Injector Solenoid Test".

      If the test ECM fixes the problem, connect the suspect ECM. If the problem returns with the suspect ECM, replace the ECM. Verify that the problem is resolved.

    STOP

Test Step 9. Check the Harness under the Valve Cover for a Short Circuit

    ------ WARNING! ------

    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.

  1. Remove the valve cover.

  1. Disconnect the harness connector for each injector solenoid that indicates a "Short" on Cat ET. Ensure that each disconnected connector does not touch other components and create a short circuit.

  1. Turn the keyswitch to the ON position.

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

Expected Result:

All of the injector solenoids that were disconnected indicate "Open" on Cat ET.

Results:

  • OK - All of the injector solenoids that were disconnected indicate "Open" on Cat ET.

    Repair: Replace the faulty injector.Perform the "Injector Solenoid Test". Verify that the problem is resolved.

    STOP

  • Not OK - At least one of the injector solenoids that were disconnected still indicate "Short" on Cat ET. There is a problem with the wiring harness inside the valve cover. There may be a problem with a connector.

    Repair: Inspect the connectors for moisture and for corrosion. Repair the wiring and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

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