C27 and C32 Tier 4 Engines Caterpillar

The following lists the probable causes of low fuel pressure:

• Fuel

• Fuel tank

• Fuel filters

• Pressure relief valve for the fuel transfer pump

• Fuel pressure sensor

• Fuel pressure regulator

• Return check valve

• Fuel lines

Use this procedure in order to troubleshoot a low fuel pressure. Use this procedure if one of the following event codes is active. Access the engine monitoring system on Caterpillar Electronic Technician (ET) in order to view the current trip points for these codes. Refer to Troubleshooting, "Engine Monitoring Parameters" for information about engine events.

Test Step 1. Determine the Code

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

2. Determine if a diagnostic trouble code is present.

Results:

• Active 5580 Code - Proceed to Test Step 2.

• Other Active Code -

  Repair: Troubleshoot the code. Refer to the proper troubleshooting procedure. Low fuel pressures may cause high fuel temperatures. Troubleshoot a code for low fuel pressure before troubleshooting a code for high fuel temperature.

  STOP

Test Step 2. Check the Fuel Level in the Tank

1. Remove the fuel tank cap from the fuel tank. Check the vent port that is in the cap for debris. Clear any restrictions with compressed air.

2. Visually inspect the fuel level in the fuel tank. Ensure that the fuel tank contains enough fuel in order to operate the engine.

3. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.

Results:

• The fuel level is OK. - Proceed to Test Step 3.

• The fuel level is not OK. -

  Repair: Fill the tank. Verify that the problem has been resolved.

  If the problem is not resolved, proceed to Test Step 3.

Test Step 3. Inspect the Fuel System for Leaks

Perform a visual inspection of the fuel system. Verify that there are no fuel leaks. Inspect the fuel lines from the fuel transfer pump to the secondary fuel filter base for restrictions.

Note: Cold weather adversely affects the characteristics of the fuel. Refer to the engines Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold-weather operation.

Results:

• No leaks were found. - Proceed to Test Step 4.

• Leaks were found in the fuel system. -

  Repair: Repair the leaks. Verify that the problem is resolved.

  If the problem is not resolved, proceed to Test Step 4.

Test Step 4. Compare the Status of Fuel Pressure in Cat ET to a Mechanical Gauge

Illustration 1	g02051497
Secondary fuel filter mounting (1) Fuel temperature sensor (2) Fuel filter differential pressure sensor (3) Fuel pressure sensor (filtered fuel pressure)

Note: Do not use the sampling port for measuring the fuel pressure.

1. Remove fuel pressure sensor (3).

2. Install a 8T-7860 Connector into the port of the pressure sensor (3).

3. Install the 110-6349 Fitting As onto the 8T-7860 Connector.

4. Install a 8T-0855 Pressure Gauge onto a 6V-3990 Coupler.

5. Install the 6V-3990 Coupler onto the 110-6349 Fitting As.

6. Record the fuel pressure on the pressure gauge. Record the data in Table 3.

Expected Result:

The value of the fuel pressure is within 137 kPa (20 psi) of the fuel pressure reading that is shown in Cat ET.

Results:

• OK - The fuel pressure readings are comparable. Proceed to Test Step 5.

• Not OK - The value of the fuel pressure is not within 137 kPa (20 psi) of the fuel pressure reading that is shown in Cat ET.

  Repair: Replace the pressure sensor. Verify that the problem has been resolved.

  If the problem is not resolved, proceed to Test Step 5.

Test Step 5. Verify that the Fuel Pressure is Within Specifications

Verify that the recorded fuel pressure is above the minimum acceptable fuel specifications. Refer to Table 4 for the minimum acceptable specifications.

Expected Result:

The fuel pressure is within specifications.

Results:

• OK - The fuel pressure is above the minimum acceptable pressure specifications. Proceed to Test Step 7.

• Not OK - The fuel pressure is not above the minimum acceptable pressure specifications. Proceed to Test Step 6.

Test Step 6. Replace the Fuel Filters

1. Replace the primary filter, the secondary filter, and the tertiary fuel filters.

   Note: The fuel system will need to be primed after the filters are replaced.

2. Verify that the fuel pressure is above the minimum acceptable pressure specifications. Refer to Table 4 for the proper specifications.

Expected Result:

The fuel pressure meets the minimum acceptable specifications.

Results:

• OK - The fuel pressure meets the minimum acceptable specifications.

  Repair: Return the engine to service.

  STOP

• Not OK - The fuel pressure does not meet the minimum acceptable specifications. Proceed to Test Step 7.

Test Step 7. Check for Air in the Fuel System

Check for air in the fuel. Refer to Systems Operation/Testing and Adjusting, "Air in Fuel - Test" for the proper procedure.

Expected Result:

The system is not contaminated with air.

Results:

• OK - Air is not found in the fuel system. Proceed to Test Step 8.

• Not OK - Air bubbles have been found in the fuel system.

  Repair: Refer to Systems Operation/Testing and Adjusting, "Air in Fuel - Test" for the proper repairs.

  If the problem is not resolved, proceed to Test Step 8.

Test Step 8. Replace the Fuel Pressure Regulator and the Return Check Valve

Illustration 2	g02140693
(4) Fuel return pressure regulator (5) Return check valve to the fuel tank

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Contact with high pressure fuel may cause fluid penetration and burn hazards. High pressure fuel spray may cause a fire hazard. Failure to follow these inspection, maintenance and service instructions may cause personal injury or death.

1. Replace the fuel return pressure regulator.

2. Inspect the return check valve for proper operation.

3. Check the fuel pressure with Cat ET.

Note: Refer to Table 4 for the proper specifications.

Results:

• The fuel pressure meets the minimum acceptable fuel pressure specifications. -

  Repair: Return the engine to service.

  STOP

• The fuel pressure does not meet the minimum acceptable fuel pressure specifications. - Proceed to Test Step 9.

Test Step 9. Inspect the Pressure Relief Valve for the Fuel Transfer Pump

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Illustration 3	g02140700
Location of the pressure relief valve for the fuel transfer pump

1. Inspect the condition of the spring for the pressure relief valve that is integral to the fuel transfer pump. The spring must move freely.

Expected Result:

The pressure relief valve and the spring are in good repair.

Results:

• OK. - The relief valve and the spring appear to be in good repair.

  Repair: Clean the relief valve and reinstall the relief valve.

  Proceed to Test Step 10.

• Not OK - The relief valve and the spring are suspect.

  Repair: Install a spring kit for the pressure relief valve. If the problem persists, replace the fuel transfer pump. Verify that the problem has been resolved.

  STOP

Test Step 10. Perform a Pump Lift Test

Perform a pump lift test on the transfer pump.

Results:

• The pump failed the pump lift test -

  Repair: Replace the transfer pump. Verify that the problem has been resolved.

  STOP