3126B Machine Engines Caterpillar

The Electronic Control Module (ECM) detects all of the following conditions:

• Fuel pressure is in the "Low Fuel Pressure Region" in Illustration 1 for ten seconds.

• The engine has been running for at least 60 seconds.

Illustration 1	g01035816
Low fuel pressure map

System Response:

The ECM will log the warning. The ECM will transmit a warning to the display in the cab. The ECM will reset the warning when the fuel pressure rises 1 kPa (0.1450 psi) above the low pressure trip line for one second.

Possible Performance Effect:

• Low power

Troubleshooting:

Test Step 1. Replace the Fuel Filter

1. Replace the fuel filter. Refer to the appropriate procedure in the Operation and Maintenance Manual for the correct procedure.

2. Start the engine and verify that the event is no longer active.

Expected Result:

Replacing the fuel filter corrected the problem.

Results:

• OK - Replacing the fuel filter corrected the problem.

  STOP

• Not OK - Replacing the fuel filter did not correct the problem. Proceed to Test Step 2.

Test Step 2. Verify Proper Sensor Installation

1. Check the installation of the fuel pressure sensor.

2. Check the wiring of the fuel pressure sensor. Refer to the Electrical Schematic for the proper wiring. Ensure that all of the wires and connectors are properly connected.

Expected Result:

The sensor is properly installed and the wiring is correct.

Results:

• OK - The sensor is properly installed. Proceed to Test Step 3.

• Not OK - The sensor is not installed properly.

  Repair: Install the fuel pressure sensor properly. Repair the wiring and/or the connectors to the sensor.

  Verify that the repair eliminates the problem.

  STOP

Test Step 3. Check for Active Diagnostic Codes

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

2. Check for active diagnostic codes that are related to the atmospheric pressure sensor and/or to the turbocharger outlet pressure sensor.

Expected Result:

There are no diagnostic codes that are related to the atmospheric pressure sensor and/or to the turbocharger outlet pressure sensor.

Results:

• OK - There are no diagnostic codes. Proceed to Test Step 4.

• Not OK - There is a diagnostic code that is related to the atmospheric pressure sensor and/or the turbocharger outlet pressure sensor.

  Repair: Troubleshoot the diagnostic code before continuing with this procedure.

  STOP

Test Step 4. Check the Status Screen

1. Place the engine control in the ON mode. The engine should be off.

2. Monitor the status for "Boost Pressure" and "Fuel Pressure" on Cat ET.

Expected Result:

"Boost Pressure" and "Fuel Pressure" are less than 10 kPa (2 psi).

Results:

• OK - The boost pressure and the fuel pressure are less than 10 kPa (2 psi). Proceed to Test Step 6.

• Not OK - Boost Pressure - The boost pressure is greater than 10 kPa (2 psi). Proceed to Test Step 5.

• Not OK - Fuel Pressure - The fuel pressure is greater than 10 kPa (2 psi). Proceed to Test Step 5.

• Not OK - Both - The boost pressure and fuel pressure are greater than 10 kPa (2 psi). Proceed to Test Step 5.

Test Step 5. Check the Supply Voltage to the Suspect Pressure Sensor(s)

1. Place the engine control in the OFF/RESET mode.

2. Disconnect the suspect sensor(s).

3. Place the engine control in the ON mode.

4. Measure the voltage between terminal A (+5V) and terminal B (Common) of each suspect pressure sensor connector on the engine harness.

Expected Result:

The voltage is 5.0 ± 0.16 VDC.

Results:

• OK - The voltage is within the range.

  Repair: Reconnect the fuel pressure sensor and the turbocharger outlet pressure sensor.

  Temporarily connect a new atmospheric pressure sensor.

  If the new sensor fixes the problem, reconnect the suspect sensor.

  If the problem returns, permanently replace the sensor.

  Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a problem with the 5 volt supply.

  Repair: Check the J2/P2 ECM connector and the sensor connectors for corrosion and for moisture.

  Check the 5 volt supply wire. Verify that the wire is not cut and that the wire is completely inserted into the connectors for the pressure sensors on the engine harness.

  Verify that the repair eliminates the problem.

  STOP

Test Step 6. Install a Pressure Gauge

1. Remove the fuel pressure sensor from the adapter fitting in the engine.

2. Install a 186-4045 Tee into the adapter fitting that is in the engine.

3. Install the fuel pressure sensor onto the 186-4045 Tee.

4. Install a 5P-5528 O-Ring Adapter into the open port in the tee fitting.

5. Connect the 1U-5470 Engine Pressure Group into the 5P-5528 O-Ring Adapter.

6. Place the engine control in the ON mode.

7. Monitor the status for "Fuel Pressure" on Cat ET.

8. Start the engine and run the engine at low idle.

9. Compare the pressure reading on the gauge to the pressure reading on Cat ET.

10. Monitor the status screen and the gauge while you increase the engine speed.

Expected Result:

The gauge and the status screen are within 35 kPa (5.0 psi) of each other.

Results:

• YES - The sensor is functioning properly.

  Repair: Compare the readings from the pressure gauge to the low fuel pressure map. There is a mechanical problem if the fuel pressure is lower than the trip line on the low fuel pressure map.

  Refer to Testing and Adjusting, "Fuel System Pressure - Test".

  STOP

• Not OK - The sensor is not functioning properly.

  Repair: Temporarily install a new sensor.

  If the new sensor repairs the problem, reinstall the suspect sensor.

  If the problem returns, replace the sensor.

  Verify that the repair eliminates the problem.

  STOP