C15 and C18 Engines for Caterpillar Built Machines Caterpillar

Fuel Pressure Is Low

Usage:

D9T NJH

The probable causes of low fuel pressure

Fuel
Fuel Tank
Fuel Filters
Fuel Transfer Pump
Fuel Pressure Sensor
Fuel Return Pressure Regulator
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. Refer to Troubleshooting, "Event Codes" for information about event codes. For information on the engine monitoring system, refer to Troubleshooting, "Engine Monitoring System".

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Table 1
Event Code
CDL Code	J1939 Code	Code Description (code descriptions may vary)	Comments
E198 (1)	5580-17	Low Fuel Pressure	The code is logged.
E198 (2)	5580-18	Low Fuel Pressure	The engine power is derated. The code is logged. The ECM will illuminate the action lamp.

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Table 2
Troubleshooting Test Steps	Values	Results
1. Determine the Code A. Connect Cat ET to the service tool connector. Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Determine if a diagnostic trouble code is present.	Diagnostic trouble code	Result: A E198 or 5580 code is present. Proceed to Test Step 2. Result: A code other than E198 or 5580 code is present. Troubleshoot the code. Refer to the proper troubleshooting procedure.
2. Check the Fuel Level in the Tank A. Visually inspect the fuel level in the fuel tank. Ensure that the fuel tank contains enough fuel in order to operate the engine. B. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.	Fuel level	Result: The fuel level is OK. Proceed to Test Step 3. Result: The fuel level is not OK. Fill the tank. Verify that the problem has been resolved. If the problem is not resolved, proceed to Test Step 3.
3. Inspect the Fuel System for Leaks A. 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.	Leaks	Result: No leaks were found. Proceed to Test Step 4. Result: Leaks were found in the fuel system. Repair the leaks. Verify that the problem is resolved. If the problem is not resolved, proceed to Test Step 4.

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Table 3
Required Tooling
8T-7860 Connector
110-6349 Fitting as
8T-0855 Pressure Gauge
6V-3990 Coupler

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Illustration 1	g02023390
(1) Fuel temperature sensor (2) Fuel sampling port (3) Fuel pressure sensor (4) Fuel filter base

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Table 4
Engine RPM	Fuel pressure from Cat ET	Fuel pressure from the mechanical gauge
800
1800

Note: Do not use the fuel sampling port (2) for measuring the pressure. Follow the steps below.

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Table 5
Troubleshooting Test Steps	Values	Results
4. Check the Fuel Pressure Sensor A. Record the fuel pressure from Cat ET. Record the data in Table 4. B. Remove fuel pressure sensor (3). C. Install an 8T-7860 Connector into the port of the pressure sensor (3). D. Install the 110-6349 Fitting as onto the 8T-7860 Connector. E. Install an 8T-0855 Pressure Gauge onto a 6V-3990 Coupler. F. Install the 6V-3990 Coupler onto the 110-6349 Fitting as. G. Record the fuel pressure on the pressure gauge. Record the data in Table 4.	Fuel Pressure Sensor	Result: The gauge value of the fuel pressure is within 137 kPa (20 psi) of the fuel pressure reading shown in ET. Proceed to Test Step 5. Result: The gauge value of the fuel pressure is not within 137 kPa (20 psi) of the fuel pressure reading shown in ET. Replace the pressure sensor. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Verify that the problem has been resolved. If the problem is not resolved, proceed to Test Step 5.

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Table 6
Engine RPM	Minimum acceptable fuel pressure
800	360 kPa (52 psi)
1800	450 kPa (65 psi)

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Table 7
Troubleshooting Test Steps	Values	Results
5. Verify that the Fuel Pressure Is Within Specifications A. Verify that the recorded fuel pressure is above the minimum acceptable fuel specifications. Refer to Table 6 for the minimum acceptable specifications.	Fuel pressure	Result: The fuel pressure is above the minimum acceptable fuel specifications. Proceed to Test Step 7. Result: The fuel pressure is not above the minimum acceptable fuel specifications. Proceed to Test Step 6.
6. Replace the Fuel Filters A. Replace the primary filter, the secondary filter, and the tertiary fuel filters. The fuel system will need to be primed after the filters are replaced. B. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Verify that the fuel pressure is above the minimum acceptable pressure specifications. Refer to Table 6 for the proper specifications.	Fuel filters	Result: The fuel pressure meets the minimum acceptable fuel pressure specifications. Return the engine to service. Result: The fuel pressure does not meet the minimum acceptable fuel pressure specifications. Proceed to Test Step 7.
7. Check for Air in the Fuel System A. Check for air in the fuel. Refer to Systems Operation/Testing and Adjusting, "Air in Fuel - Test" for the proper procedure.	Air	Result: Air is in the system. 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. Result: Air is not in the system. Proceed to Test Step 8.

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Illustration 2	g02025071
(5) Anti-drain check valve (6) Fuel return pressure regulator

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Table 8
Troubleshooting Test Steps	Values	Results
8. Replace the Fuel Return Pressure Regulator A. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position. Replace the fuel return pressure regulator. B. Inspect the anti-drain check valve (5) for proper operation. C. Check the fuel pressure with Cat ET. Refer to Table 6 for the proper specifications.	Fuel return pressure regulator	Result: The fuel pressure meets the minimum acceptable fuel pressure specifications. Return the engine to service. Result: The fuel pressure does not meet the minimum acceptable fuel pressure specifications. Proceed to Test Step 9.
9. Replace the Transfer Pump A. Replace the transfer pump.	Transfer pump	Result: The transfer pump was replaced. Reset all active codes and clear all logged codes by cycling the keyswitch to the Off position Verify that the problem has been resolved.

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

If the procedure corrected the issue, return the engine to service.

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).