3176C and 3406E Engines for D7R Series II and D8R Series II Track-Type Tractors Caterpillar


Low Power/Poor or No Response to Throttle

Usage:

D8R II 6YZ

Probable Causes

  • Active engine derate

  • Cold mode

  • Throttle switch

  • Decelerator pedal

  • Electrical connectors

  • Unit injectors

  • Turbocharger outlet pressure sensor

  • Air inlet and exhaust system

  • Parameters

  • Fuel supply

Recommended Actions

Active Engine Derate

Use Caterpillar Electronic Technician (ET) to check for logged engine derates and/or active engine derates. A derate status flag will appear on Cat ET if an active engine derate is occurring. The engine may be derated due to one of the following conditions: high altitude, dirty air filters and other factors.

Cold Mode

  1. Use Cat ET to verify that the engine has exited cold mode. Cold mode operation may cause the engine to run rough and engine power may be limited.

  1. Observe the coolant temperature on the Cat ET status screen. Verify that the reading is valid.

Throttle Switch

Monitor the throttle switch on Cat ET. Verify that the throttle switch is operating correctly. Refer to Troubleshooting, "Throttle Switch Circuit - Test" for the proper troubleshooting procedure.

Decelerator Pedal

Monitor the decelerator pedal on Cat ET. Verify that the decelerator pedal is operating properly. Refer to Troubleshooting, "Decelerator Position Sensor Circuit - Test" for the proper troubleshooting procedure.

Electrical Connectors

Check for correct installation of the J1/P1 and J2/P2 connector and the unit injector connectors for the Electronic Control Module (ECM). Refer to Troubleshooting, "Electrical Connectors - Inspect".

Unit Injectors

  1. Use Cat ET to determine if there are any active diagnostic codes for the unit injectors.

  1. Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM.

  1. Perform the "Cylinder Cutout Test" on Cat ET in order to identify any misfiring cylinder(s). Refer to Troubleshooting, "Injector Solenoids Circuit - Test" for more information.

Turbocharger Outlet Pressure Sensor

  1. Monitor the status of "Fuel Position", "Rated Fuel Limit", and "FRC Fuel Limit" on Cat ET while the engine is operating under full load. These parameters should 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.

  1. Monitor the status of "Boost Pressure" and "Atmospheric Pressure" for normal operation on Cat ET. When the engine is not running, "Boost Pressure" should be 0 kPa (0 psi).

Air Inlet and Exhaust System

  1. Observe the check engine lamp. Check for an air filter restriction indicator. Clean plugged air filters or replace plugged air filters. Refer to the Operation and Maintenance Manual.

  1. Check the air inlet and exhaust system for restrictions and/or leaks. Refer to Testing and Adjusting, "Air Inlet and Exhaust System".

Parameters

If the ECM has been replaced, compare the values on the engine information plate to the following parameters from Cat ET:

  • Fuel Ratio Control (FRC) offset.

  • Full Load Setting (FLS)

  • Full Torque Setting (FTS)

Fuel Supply

  1. 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.

  1. Check the fuel tank for foreign objects which may block the fuel supply.

  1. Check for air in the low pressure 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

    Note: A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel. Refer to Testing and Adjusting for more information.


    NOTICE

    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.


  1. Purge air from the low pressure fuel supply circuit. Refer to Operation and Maintenance Manual, "Fuel System - Prime" for the correct procedure.

  1. Check fuel quality. In temperatures below 0 °C (32 °F), check for solidified fuel (wax). Refer to Special Instruction, SEBD0717, "Diesel Fuels And Your Engine".

  1. Check the fuel pressure after the fuel filter while the engine is being cranked. Refer to 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. Refer to Testing and Adjusting for more information.

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