3512C and 3516C Marine Auxiliary Engines Caterpillar

Fuel Pressure Is High

Usage:

Use this procedure in order to troubleshoot a problem with the fuel system.

Probable Causes

Fuel pressure sensor
Fuel lines
Fuel transfer pump
Fuel return pressure regulator

Recommended Actions

Note: High fuel pressure may cause high fuel temperatures. Troubleshoot a code for high fuel pressure before troubleshooting a code for high fuel temperature.

Note: The procedures have been listed in order of probability. Complete the procedures in the order of the listed test steps.

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Table 1
Troubleshooting Test Steps	Values	Results
1. Active Codes and Logged Codes A. Establish communication between Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM). B. Monitor the diagnostic codes on Cat ET. Check for active or logged diagnostic codes. Specifically check for codes that could be associated to poor acceleration. Refer to the histogram information for engine derates in Cat ET. Note: Wait at least 30 seconds in order for diagnostic codes to become active. C. If the histograms contain derates and no diagnostic codes are present, then the engine is operating normally.	Diagnostic trouble code	Result: A diagnostic code is present. Repair: Troubleshoot any codes before continuing with this procedure. Verify that the repair eliminated the problem. Reset the histogram. Result: A diagnostic code is not present. Proceed to Test Step 2.
2. Check the Fuel Pressure Sensor A. Record the fuel pressure from Cat ET. Use a mechanical gauge to check the system fuel pressure. Refer to Systems Operation/Testing and Adjusting, "Fuel System" for additional information. G. Record the fuel pressure on the pressure gauge. Note: If a mechanical gauge is not available, determine if the fuel pressure reading on Cat ET is reasonable.	Fuel pressure	Result: The gauge value of the fuel pressure is reasonable when compared to the fuel pressure reading shown in ET. Proceed to Test Step 3. Result: The gauge value of the fuel pressure is not reasonable when compared to the fuel pressure reading shown in ET. Repair: Replace the pressure sensor. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Verify that the repair eliminated the problem.
3. Inspect the Fuel Supply Lines A. Visually inspect the fuel lines. Also, inspect the fuel cooler, if equipped. Inspect the fuel return line from the head to the fuel tank. Inspect the lines for restrictions, pinching, and swelling.	Restrictions, pinching, and swelling	Result: The fuel lines and the cooler (if equipped) are OK. Proceed to Test Step 4. Result: The fuel lines and the cooler (if equipped) are not OK. Repair: Make the necessary repairs. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Verify that the repair eliminated the problem.
4. Replace the Return Fuel Pressure Regulator A. Replace the fuel pressure regulator.	Fuel pressure regulator	Result: The regulator was replaced. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Verify that the repair eliminated the problem.
5. Inspect the Relief Valve for the Fuel Transfer Pump A. Inspect the relief valve for the transfer pump. The spring must move freely.	Relief valve	Result: The relief valve is stuck closed. Repair: Replace the fuel transfer pump. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Verify that the repair eliminated the problem. Result: The relief valve is OK. Clean the relief valve and reinstall the relief valve. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Verify that the repair eliminated the problem.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).