8M0043790 Mercury HOSE, Hi-Pressure Filter To Fuel Rail

Probable Causes
Fuel supply
Derates
Throttle signal
Engine speed/timing sensor(s)
Turbocharger
Rated fuel position
Air inlet and exhaust restrictions
Power supply for the Electronic Control Module (ECM)
Fuel position multiplier (if applicable)Recommended Actions
Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine speed, full load and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.Fuel Supply
Check the fuel level in the fuel tank. Ensure that adequate fuel is available for the application.Check fuel lines for the following problems: restrictions, collapse and pinched line. Repair the lines and/or replace the lines.
Check the fuel tank for foreign objects which may block the fuel supply. Check for air leaks in the suction line of the fuel pump. Prime the fuel system after you perform the following procedures:
Replacing the fuel filters
Working on the low pressure fuel supply circuit
Replacing fuel injectors
Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold weather operation.
Check the fuel pressure during engine operation. Check the fuel pressure after the fuel filter. Refer to the Systems Operation/Testing and Adjusting manual for the correct pressure values. If the fuel pressure is low, replace the fuel filters. If the fuel pressure is still low, check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve. Derate
Connect Caterpillar Electronic Technician (ET) and check for an active derate event. A derate status flag will appear on Cat ET if an active engine derate is occurring. In order to view active events, go to the "Events" menu under "Diagnostics".Throttle Signal
Use Cat ET in order to monitor the status of the throttle. Observe the throttle position. Verify that the throttle position is smooth from low idle to high idle. The throttle position should reach 100 percent at high idle.Engine Speed/Timing Sensor(s)
If the following diagnostic codes are applicable, check Cat ET for any logged diagnostic codes for the primary engine speed/timing sensor: 190-02, 190-03 and 190-08. If the engine is equipped with a secondary engine speed/timing sensor, check for any of the following logged diagnostic codes: 342-02, 342-03 and 342-08. Refer to the diagnostic functional test Troubleshooting, "Engine Speed/Timing Sensor".Turbocharger
Ensure that the turbocharger is operating correctly. Periodic inspection and cleaning is recommended for the turbocharger compressor housing (inlet side).Rated Fuel Position
Operate the engine under full load. Use Cat ET in order to monitor the following values: turbocharger compressor outlet pressure, fuel position, rated fuel position and Fuel Ratio Control (FRC). The fuel position should equal the rated fuel position. The FRC fuel position should be greater than the rated fuel position.If any of the above values are changing rapidly for no apparent reason, there may be an intermittent problem with the wiring. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".Air Inlet and Exhaust Restrictions
Check the air inlet system for the following problems: restrictions, collapse and pinched line. Repair the lines and/or replace the lines.Check for an air filter restriction indicator. Replace plugged air filters and/or clean filters. Repair any leaks.ECM Power Supply
Inspect the circuit between the ECM and the batteries. Refer to the Electrical System Schematic. Inspect the wires, the connectors, and the components in the circuit. Refer to Troubleshooting, "Electrical Power Supply" for more information.
Inspect the circuit between the ECM and the keyswitch. Refer to the Electrical System Schematic. Inspect the wires, the connectors, and the components in the circuit. Refer to Troubleshooting, "Electrical Power Supply" for more information. Fuel Position Multiplier (if applicable)
If equipped, use Cat ET to verify that the fuel position multiplier is not affecting the available fuel rack. Refer to the diagnostic procedure Troubleshooting, "Fuel Position Multiplier".