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No Rail Fuel Pressure (Low Fuel Pressure) - Event Code: SPN 94 - FMI 17

SPN94 FMI17 (C7 Engine) 

Figure 1.1 - SPN 94 FMI 17 (Murphy PowerView)

E198(1) Low Fuel PressureThe fuel pressure drops below 175 kPa (25 psi) for 10 seconds. 
E198(2) Low Fuel PressureThe fuel pressure drops below 150 kPa (22 psi) for 15 seconds. 

#Probable Causes:
  • Fuel Supply
  • Diagnostic Codes and Event Codes
  • Fuel Pressure Sensors
  • Fuel Pressure Regulating Valve
  • Fuel Priming Pump (if equipped)
  • Fuel Transfer Pump
  • Injection Actuation Pressure

#Recommended Actions:
1). Fuel Supply
Visually check the fuel level. Do not rely on the fuel gauge only. If necessary, add fuel. If the Engine has been run out of fuel, it will be necessary to prime the fuel system.
Check the fuel lines for the following problems: restrictions, collapsed lines and pinched lines. If problems are found with the fuel lines, repair the lines and/or replace the lines.
Check the fuel tank for foreign objects which may block the fuel supply.
Prime the fuel supply system if any of the following procedures have been performed:
  • Replacement of the fuel filters
  • Service on the low pressure fuel supply circuit
  • Replacement of unit injectors
Check fuel flow after the fuel filters. If the fuel flow is low, replace the fuel filters.

2). Diagnostic Codes and Event Codes
Connect Cat ET to the service tool connector. Check for active Diagnostic Codes and Event Codes. Look for active Diagnostic Codes that are related to the low pressure fuel system. Read More: How to Connecting Caterpillar ET Software to the ECM.
Figure 1.2 - Logged Event Codes

3). Fuel Pressure Sensor
Start the Engine. In this case, Engine cranks but doesn't STARTS (Fuel Pressure: 2-42 Psi).
→Use Cat ET to monitor the "Fuel Pressure" for the Engine. Ensure that the value of the parameter is reasonable. Read More: Status Tool on Caterpillar ET Software.
Figure 1.3 - Fuel Pressure (42 Psi)
If a problem with the sensor is suspected, replace the suspect sensor.

4). Fuel Pressure Regulating Valve
A Fuel Pressure Regulating Valve that is stuck in the open position may cause low fuel pressure. If a problem with the valve is suspected, the problem is probably caused by contamination or debris lodged between the valve and the valve seat. Remove the valve assembly from the fuel filter base. Inspect the valve assembly for contamination or debris. Clean any contamination or debris that may keep the regulating valve open. If debris is present, find the source of the contamination.
If the Fuel Pressure Regulating Valve is the suspected cause of the low fuel pressure, replace the valve assembly.

5). Fuel Priming Pump (If Equipped)
The electric Fuel Priming Pump is used to prime the low pressure fuel system. Ensure that the electric Fuel Priming Pump is achieving the correct pressure.

6). Fuel Transfer Pump
The Fuel Transfer Pump may not be pumping an adequate volume of fuel in order to maintain the correct pressure in the low pressure fuel system. If the correct pressure in the low pressure fuel system is not maintained during start-up the Engine will start, but the Engine will not continue running.
Use Cat ET to monitor the "Fuel Pressure" status parameter during Engine starting. Read More: Real Time Graphing using Caterpillar ET Software.
Figure 1.4 - Engine cranks, but doesn't starts
If the other components in the fuel system are operating within specifications, and the fuel pressure decreases after starting the Engine, replace the Fuel Transfer Pump.
Figure 1.5 - Normal Starts (Fuel Pressure: 68 Psi)

7). Injection Actuation Pressure
Check the Engine oil level. Engine oil supplies the Injection Actuation Pressure circuit. The Engine oil must be kept at the proper level for fuel injection.
If service has recently been performed on the Engine, air may be present in the Injection Actuation Pressure circuit. Allow the Engine to fully warm up and operate the Engine under load in order to purge the air from the Injection Actuation Pressure circuit.
Check the Injection Actuation Pressure. Read More: Injection Actuation Pressure Test using Caterpillar ET Software.
Check the operation of the Injection Actuation Pressure control valve.











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