823420A03 Mercury DECAL SET (Gray 90)

Probable Causes
Diagnostic codes and event codes
Electrical connectors or power supply
Fuel supply
Cold mode operation and cold cylinder cutout
Throttle signal
Fuel quality
Air intake and exhaust system
Governor gain settings
Cylinder performance
InjectorsRecommended Actions
Diagnostic Codes and Event Codes
Check for active diagnostic codes on Caterpillar Electronic Technician (ET). Troubleshoot any active codes before continuing with this procedure.Electrical Connectors or Power Supply
There may be an intermittent interruption of power that is causing the symptom. Check the wiring harnesses and the connectors. Inspect the connectors in each of the terminal boxes. Inspect the power supply connections and the ground connections.Inspect the wiring from the power supply to the Electronic Control Modules (ECM). Refer to Troubleshooting, "Electrical Power Supply - Test" for information that is related to the wiring harnesses and connectors.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, purge the air from the fuel system. Refer to Operation and Maintenance Manual for more information.
Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
Check the fuel lines for the following problems: restrictions, collapsed lines, pinched lines and loose connections. If problems are found with the fuel lines, repair the lines and/or replace the lines.
Air in the fuel can cause the engine to run rough. 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.
Check the fuel tank for foreign objects which may block the fuel supply.
Check the fuel filters.
Check the diesel fuel for contamination.
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. Cold Mode Operation and Cold Cylinder Cutout
Use Cat ET in order to verify that the engine has exited cold mode. During cold mode, fuel injection timing is modified. When the engine is in cold mode, the cold cylinder cutout strategy may be active. Cold mode cylinder cutouts may cause variations in vibration and available power. The variations in vibration and available power is normal operation.Throttle Signal
Monitor the throttle signal on Cat ET. Verify that the throttle signal is smooth from the low idle position to the high idle position. Refer to Troubleshooting, "Speed Control - Test".Fuel Quality
Check the fuel quality. For further information, refer to the engine Operation and Maintenance Manual.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. Governor Gain Settings
Improper governor gain settings can cause the engine to become unstable. Refer to Troubleshooting, "Configuration Parameters" for information that is related to the governor gain for your engine.Cylinder Performance
Check the valve lash and reset the valve lash, if necessary. Refer to Systems Operation/Testing and Adjusting. Injectors
Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM.
Perform the "Cylinder Cutout Test" on Cat ET in order to determine the performance of each cylinder. Refer to Troubleshooting, "Injector Solenoid - Test" for the proper procedure.