C9.3 Tier 4 Final Engines Caterpillar

Fuel Rail Pressure Is Low

Usage:

D6T 2B3

Note: Refer to Troubleshooting, "Cat ET Service Features" for information about service features.

Use this procedure in order to troubleshoot low fuel rail pressure or use this procedure if the following event code is active. Refer to Troubleshooting, "Event Codes" for information about event codes. For information on the engine monitoring system, refer to Troubleshooting, "Engine Monitoring System".

Note: Some of the following codes may not be applicable for certain applications.

Note: The E398 code may activate when the water separator is being drained. Disregard the code and toggle the keyswitch to clear the code.

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Table 1
Diagnostic Trouble Codes
J1939 Code	CDL Code	Code Description	Comments
157-17	E398 (1)	Low Fuel Rail Pressure	The fuel rail pressure is below an acceptable level. The code is logged. The check engine light will illuminate.

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Table 2
Associated Diagnostic Trouble Codes
J1939 Code	CDL Code
157-3	1797-3
157-4	1797-4
5584-15	E390 (1)
5584-16	E390 (2)
1347-5	1779-5
1347-6	1779-6
1348-5	1780-5
1348-6	1780-6
5580-17	E198 (1)
5580-18	E198 (2)

Troubleshooting Procedure

Complete the procedure in the order in which the steps are listed.

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Table 3
Troubleshooting Test Steps	Values	Results
1. Check for Associated Codes A. Establish communication between Cat^® Electronic Technician (ET) and the Engine Electronic Control Module (ECM). B. Download the "Warranty Report" from the engine ECM before performing any troubleshooting or clearing diagnostic trouble codes. C. If any of the associated codes in Table 2 are logged, troubleshoot the codes before continuing with this procedure.	Associated Codes	Result: An associated code is active or logged. Repair: Troubleshoot the associated codes before continuing with this procedure. Result: An associated code is not active or logged. Proceed to Test Step 2.
2. Inspect the Fuel System A. Inspect the fuel system. Refer to Systems Operation/Testing and Adjusting, "Fuel System - Inspect" for inspection of the high-pressure fuel lines and the fuel rail.	Fuel System Problems	Result: Problems were found with the fuel system. Repair: Repair the components or replace the components that are damaged. Verify that the problem is resolved. Result: Problems were not found with the fuel system. Proceed to Test Step 3.
3. Check the Fuel Rail Sensor A. Allow the engine to be OFF for 10 minutes. B. Turn the keyswitch to the ON position, do not start the engine. C. Connect to the Engine ECM using Cat ET. D. Using Cat ET, check the status of the "Fuel Rail Pressure (absolute)".	Rail pressure less than 5,000 kPa (725 psi)	Result: The pressure dropped below 5,000 kPa (725 psi) after the engine was shut off for 10 minutes. Proceed to Test Step 4. Result: The pressure did not drop below 5,000 kPa (725 psi) after the engine was shut off for 10 minutes. Repair: Replace the fuel rail pressure sensor. If the problem has been corrected, return the unit to service.
4. Start the Engine A. Try to start the engine.	Engine will Start	Result: The engine will start. Proceed to Test Step 5. Result: The engine will not start. Repair: Refer to Systems Operations/Testing and Adjusting, "Injector Bypass Fuel Flow"

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Illustration 1	g03383455
Location of the "Fuel System Functional Test" in the "Diagnostic Service Test" menu

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Illustration 2	g03383456
If an E398 Low Fuel Rail Pressure fault is active, the "Fuel System Functional Test – Pretest" will not be able to run. Uncheck the "Fuel System Functional Test – Pretest" box and proceed to the "Fuel System Functional Test"

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Table 4
Troubleshooting Test Steps	Values	Results
5. Perform the "Fuel System Functional Test" A. Start the engine. B. Connect to the Engine ECM using Cat ET. C. Perform the "Fuel System Functional Test" in Cat ET. Cat ET will display an error message that indicates the problem. Follow the repair procedure for the error message. If the test aborts for an active diagnostic make sure to troubleshoot the code first. If an E398 Low Fuel Rail Pressure fault is active, the "Fuel System Functional Test – Pretest" will not be able to run. Uncheck the box and proceed to the "Fuel System Functional Test".	Test Passed	Result: The test failed for an $1120 - Fuel Pump Not Timed Correctly Repair: Remove the high-pressure fuel pump. Refer to Disassembly and Assembly for the correct procedures. Pin the engine to TDC. Time the pump and then reinstall the high-pressure fuel pump. Then, run the "Fuel System Functional Test" in order to verify that the pump is timed correctly. Result: The test failed for an $111F - Fuel Flow Too Low Repair: Replace the high-pressure fuel pump. Refer to Disassembly and Assembly for the correct procedure. Then, run the "Fuel System Functional Test" again in order to verify that the problem is resolved. Result: The test failed for an $111D - Fuel Rail High Pressure Decay Too High Repair: Replace the relief valve. Refer to Disassembly and Assembly for the correct procedure. Then, run the "Fuel System Functional Test" again in order to verify that the problem is resolved. If the problem is not resolved, torque all the quill tubes again, then perform the "Fuel System Functional Test". If the test passed, return the unit to service. If the test failed, perform the "Injector Bypass Fuel Flow - Test". Refer to Systems Operation/Testing and Adjusting, "Injector Bypass Fuel Flow - Test". Result: The test failed for an $111E - Fuel Rail Low Pressure Decay Too High Repair: Torque all the quill tubes again, then perform the "Fuel System Functional Test". If the test passed, return the unit to service. If the test failed, perform the "Injector Bypass Fuel Flow - Test". Refer to Systems Operation/Testing and Adjusting, "Injector Bypass Fuel Flow - Test". Result: The test passed successfully. Contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).