C4.4 and C6.6 Industrial Engines and Engines for Caterpillar Built Machines Caterpillar

Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:

• 1779-05 Fuel Rail #1 Pressure Valve Solenoid current below normal

• 1779-06 Fuel Rail #1 Pressure Valve Solenoid current above normal

Note: The fuel rail pump is installed on the engine at the factory. The fuel rail pump is not a serviceable part. The fuel rail pump delivers fuel into the fuel rail at very high pressure.

Use this procedure to troubleshoot the system when there is a active diagnostic code or if a diagnostic code can easily be activated.

The fuel rail pump solenoid is used to control the output from the fuel rail pump. The solenoid receives an electrical supply from the ECM. The fuel rail pump solenoid is then energized when the fuel is required to be pumped into the fuel rail. Varying the timing of the voltage to the solenoid controls the fuel delivery from the fuel rail pump.

When the fuel rail pump solenoid is deactivated, the fuel that is not sent to the fuel rail is returned to the fuel tank.

The fuel rail pump solenoid forms part of the closed loop control system for the fuel rail pressure in conjunction with the fuel rail pressure sensor, the ECM and the software. The fuel rail pressure sensor measures the fuel pressure in the high pressure fuel rail. The signal from the fuel rail pressure sensor is processed by the ECM and software. The measured pressure is compared to the desired fuel rail pressure for the given engine operating conditions.

If the fuel rail pump solenoid fails, it is likely that the fuel will not be pumped into the high pressure fuel rail. The engine will shut down or the engine will fail to start. The fuel rail pressure can be observed on the status screen of the electronic service tool.

Illustration 1	g01803553
Typical schematic of the circuit for the fuel rail pump solenoid

Illustration 2	g01803554
Typical view of the pin locations on theP2 connector for the fuel rail pump solenoid (25) Fuel rail pump solenoid PWM signal (26) Fuel rail pump solenoid return

Test Step 1. Inspect the Electrical Connectors and the Harness

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Electrical shock hazard. The fuel rail pump solenoid uses 63 to 73 volts.

1. Turn the keyswitch to the OFF position.

2. Thoroughly inspect the harness connector P2/J2 and the suspect connector P532. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the solenoid connector P532 and the connector pins 25 and 26 that are associated with the fuel rail pump solenoid. Refer to illustration 2.

4. Check the harness for abrasions and for pinch points from the battery to the ECM. Check the harness for abrasions and for pinch points from the key switch to the ECM.

5. Use the electronic service tool in order to perform a "Wiggle Test". The "Wiggle Test"is used to identify intermittent connections.

Expected Result:

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

Results:

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

• Not OK - There is a fault with the connectors and/or the harness.

  Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair has eliminated the fault.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect the electronic service tool to the diagnostic connector.

2. Turn the keyswitch to the ON position.

3. Use the electronic service tool to verify if any of the following diagnostic codes are active or recently logged:
   • 1779-05 Fuel Rail #1 Pressure Valve Solenoid current below normal

   • 1779-06 Fuel Rail #1 Pressure Valve Solenoid current above normal

Expected Result:

One or more of the following diagnostic codes are active or recently logged:

• 1779-05 Fuel Rail #1 Pressure Valve Solenoid current below normal

• 1779-06 Fuel Rail #1 Pressure Valve Solenoid current above normal

Results:

• 1779-05 - Proceed to Test Step 3.

• 1779-06 - Proceed to Test Step 7.

• Not OK - No active diagnostic codes or recently logged diagnostic codes are displayed.STOP

Test Step 3. Check the Harness for an Open Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect P2 from the ECM.

3. Measure the resistance betweenP2:25 and P2:26.

Expected Result:

The nominal resistance is less than 2.0 Ohms.

Results:

• OK - The harness and the solenoid do not have an open circuit.

  Repair: Check the high pressure fuel system for leaks. A mechanical relief valve is installed in the high pressure fuel rail. Check that there is no flow of fuel from the mechanical relief valve. Refer to the Operation and Maintenance Manual, "High Pressure Fuel Lines".If the fuel system is not OK, repair the fuel system and restart the diagnostic process.

  If the fuel system is OK, proceed to Test Step 4.

• Not OK - There is an open circuit. Proceed to Test Step 4.

Test Step 4. Check the Fuel Rail Pump Solenoid for an Open Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector from the fuel rail pump solenoid.

3. Measure the resistance of the fuel rail pump solenoid.

Expected Result:

The nominal resistance is less than 1.0 Ohms.

Results:

• OK - There is an open circuit or there is an excessive resistance in the harness.

  Repair: Repair the connectors or the harness and/or replace the connectors or the harness.Ensure that all of the seals are correctly in place and ensure that all connectors are correctly coupled.Use the electronic service tool in order to clear all logged diagnostic codes.Use the electronic service tool in order to perform the fuel rail pump solenoid test.Verify that the repair eliminated the fault.

  STOP

• Not OK - The fuel rail pump solenoid is faulty.

  Repair: Temporarily connect a new fuel rail pump to the harness, but do not install the fuel rail pump to the engine.Reconnect the P2 to the ECM. Check the screw for the ECM connector for the correct torque of 5.0 N·m (44 lb in).Use the electronic service tool in order to perform the fuel rail pump solenoid test.Verify that the repair eliminated the fault.If the diagnostic code has been cleared, install the new fuel rail pump to the engine. Refer to Disassembly and Assembly Manual, "Fuel Injection Pump - Install".

  STOP

Test Step 5. Check the Fuel Rail Pump Solenoid for a Short Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector from the fuel rail pump solenoid.

3. Turn the keyswitch to the ON position.

4. Use the electronic service tool in order to perform the fuel rail pump solenoid test.

Expected Result:

A Current Below Normal diagnostic code is displayed. The Current Above Normal diagnostic code is not displayed.

Results:

• OK - A Current Below Normal diagnostic code is displayed. The harness has no shorts to supply or ground. The fuel rail pump solenoid is faulty.

  Repair: Temporarily connect a new fuel rail pump to the harness, but do not install the fuel rail pump to the engine.Reconnect P2 to the ECM. Check the screw for the ECM connector for the correct torque of 5.0 N·m (44 lb in).Use the electronic service tool in order to clear all logged diagnostic codes.Use the electronic service tool in order to perform the fuel rail pump solenoid test.Verify that the repair eliminates the fault.If the diagnostic code has been cleared, then install the new fuel rail pump to the engine. Refer to Disassembly and Assembly, "Fuel injection Pump - Remove" and Disassembly and Assembly, "Fuel injection Pump - Install".

  STOP

• Not OK - The harness has a short circuit or the ECM has a short circuit. Proceed to Test Step 6.

Test Step 6. Check the harness for the Fuel Rail Pump Solenoid for a Short Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the P532 connector from the fuel rail pump solenoid.

3. Disconnect the P2 connector from the ECM.

4. Measure the resistance between P2:26 and P2:25.

5. Measure the resistance between P2:25 and voltage +.

6. Measure the resistance between P2:25 and the voltage (-).

7. Measure the resistance between P2:26 and voltage +.

8. Measure the resistance between P2:26 and voltage (-).

Expected Result:

The resistance is greater than 20,000 Ohms.

Results:

• OK - The harness has no short circuit to supply or ground. The ECM is suspect. Proceed to Test Step 7.

• Not OK - The harness has a short circuit.

  Repair: Repair the harness and connectors or replace the faulty harness and connectors.Connect the P532 connector to the fuel rail pump solenoid.Connect the P2 connector to the ECM.Turn the keyswitch to the ON position.Use the electronic service tool in order to perform the fuel rail pump solenoid test.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair has eliminated the fault.

  STOP

Test Step 7. Check the ECM and the Harness

1. Turn the keyswitch to the OFF position.

2. Disconnect the P532 connector from the fuel rail pump solenoid.

3. Insert a jumper wire across P532.

4. Turn the keyswitch to the ON position.

5. Use the electronic service tool in order to perform the fuel rail pump solenoid test.

6. Use the electronic service tool in order to monitor the status screen.

Expected Result:

Diagnostic code 1779-6 is displayed.

Results:

• OK - The ECM and the ECM connections function. The solenoid is not an open circuit. Recheck the diagnostic codes. Proceed to Test Step 5.

• Not OK - The ECM is suspect. Proceed to Test Step 8.

Test Step 8. Check the ECM Function

1. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

2. Contact the Technical Communicator.

   Note: This consultation can greatly reduce the repair time.

3. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

4. Use the electronic service tool to recheck the system for active diagnostic codes.

Expected Result:

The fault is eliminated.

Results:

• OK - The fault is eliminated with the test ECM.

  Repair: Perform the following procedure:

  1. Reconnect the suspect ECM.

  2. If the fault returns with the suspect ECM, replace the ECM.

  3. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

• Not OK -

  Repair: Repeat the test procedure from Test Step 1.

  STOP