853141 Mercruiser NUT, (M5)

Probable Causes
Diagnostic codes
Event codes
Electrical connectors
Electronic Control Module (ECM)
Fuel supply
Air intake and exhaust systemRecommended Actions
Diagnostic Codes and Event Codes
Certain diagnostic codes and/or event codes may cause poor performance. Connect the Caterpillar Electronic Technician (ET) and check for active codes and/or for logged codes. Troubleshoot any active codes before continuing with this procedure.Electrical Connectors
Thoroughly inspect the P2/J2 and P1/J1 harness connectors. Thoroughly inspect the connectors that are associated with the power supply circuit and the fuel supply circuit. Refer to service Troubleshooting, "Electrical Connectors - Inspect".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 purge the air from the fuel system. Refer to Operation and Maintenance Manual.
Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
Contact with high pressure fuel may cause fluid penetration and burn hazards. High pressure fuel spray may cause a fire hazard. Failure to follow these inspection, maintenance and service instructions may cause personal injury or death.
Do not loosen any high pressure fuel lines when the engine is running. The high pressure in the fuel lines can cause personal injury or death. Wait 60 seconds after the engine has stopped to allow pressure to purge before any service or repair is performed on the engine fuel lines.
Check the fuel lines for the following problems: restrictions, collapsed lines, pinched lines and loose connections. If problems are found with the low pressure fuel lines, repair the lines and/or replace the lines. If the high pressure fuel lines have a leak, the high pressure fuel lines must be replaced. Refer to the Disassembly and Assembly manual.
Do not crank the engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again.
Prime the fuel 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 injectorsNote: A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel. Refer to Systems Operation/Testing and Adjusting.
Check the fuel tank for foreign objects which may block the fuel supply.
Check the fuel filters.
Check the diesel fuel for contamination. Refer to Systems Operation/Testing and Adjusting.
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.
Do not crank the engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again.
Check the fuel pressure after the fuel filter while the engine is being cranked. Refer to Systems Operation/Testing and Adjusting 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.Air Intake and Exhaust System
Check the air filter restriction indicator, if equipped. Clean plugged air filters or replace plugged air filters. Refer to the Operation and Maintenance Manual.
Check the air inlet and exhaust system for restrictions and/or leaks. Refer to Systems Operation/Testing and Adjusting.