843797 Volvo.Penta Nut

Probable Causes
Configuration parameters
Diagnostic codes and events
Low idle switch
Intake manifold pressure sensor and atmospheric pressure sensor
Fuel supply
Air inlet and exhaust system
Accessory equipmentRecommended Actions
Configuration Parameters
Use Caterpillar Electronic Technician (ET) to check for the correct settings of the configuration parameters. Check that the engine is configured correctly for your application. Check the settings of the following parameters: "Droop/Isochronous Switch Enable", "Droop mode selection", "Desired Speed Input Configuration" and "Secondary Desired Speed Input Configuration". Refer to Troubleshooting, "Configuration Parameters" for details.Diagnostic Codes and Events
Use Cat ET to check for logged derates. The engine speed or the engine power may be limited due to one of the following conditions: high altitude, high intake manifold air temperature, low oil pressure, air filter restriction and other factors. Refer to Troubleshooting, "Event Codes List" for the specific events that are applicable to this application.Low Idle Switch
Monitor the switch signal on Cat ET. Verify that the signal is stable at the low idle position. Verify that the signal is stable at the high idle position. Move the switch from the low idle position to the high idle position in order to verify that the engine is able to reach the high idle position. Refer to Troubleshooting, "Switch Circuits - Test" for troubleshooting information.Intake Manifold Pressure Sensor and Atmospheric Pressure Sensor
Monitor the status of "Fuel Position", of "Rated Fuel Limit", and of "FRC Fuel Limit" on Cat ET while the engine is operating under full load. These parameters must reflect the information below.
Table 1
"Fuel Position" = "Rated Fuel Limit"
and
"Fuel Position" < "FRC Fuel Limit"    If "Fuel Position" equals "Rated Fuel Limit" and "Fuel Position" is less than "FRC Fuel Limit", the electronics are operating correctly. Otherwise, proceed with the next Step.
Use Cat ET in order to monitor the status of the "Boost Pressure". With the engine stopped, the correct "Boost Pressure" is 0 kPa (0 psi).
Start the engine and monitor the status of "Boost Pressure" while you vary the engine speed. Ensure that the pressure reading is fluctuating with the engine speed.
Use Cat ET in order to check the status of the "Atmospheric Pressure". Verify that the pressure reading is reasonable for the current conditions.Fuel Supply
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 or debris which may block the fuel supply.
Prime the fuel system if any of the following items have been serviced recently:
Fuel filters
Low pressure fuel supply circuit
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, "Air in Fuel - Test" for more information.
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.
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 cranking. Refer to Systems Operation/Testing and Adjusting, "Fuel System" for the correct procedure. If the fuel pressure is below specifications, replace the fuel filters. If this does not correct the problem, check for the proper operation of the following items: fuel transfer pump, fuel pressure relief valve and fuel pressure regulator valve.Air Inlet and Exhaust System
Check for an air filter restriction indicator. 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, "Air Inlet and Exhaust System".Accessory Equipment
Check all accessory equipment for problems that may create excessive load on the engine. Make the necessary repairs to damaged components. Replace parts, if necessary.