3456 Engine, 836G Landfill Compactor, 834G Wheel Dozer and 988G Wheel Loader Caterpillar

Probable Causes

• Diagnostic codes and event codes

• Cold mode

• Throttle signal

• Electrical connectors

• Unit injectors

• Turbocharger outlet pressure sensor

• Air inlet and exhaust system

• Parameters

• Fuel supply

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.

Diagnostic Codes and Event Codes

Certain diagnostic codes and/or event codes may cause poor performance. Connect the Caterpillar Electronic Technician (Cat ET) and check for active codes and/or for logged codes. Troubleshoot any codes that are present before continuing with this procedure.

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.

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

Throttle Signal

Monitor the status for "Throttle Position" on Cat ET. Verify that the status for "Throttle Position" is stable and that the engine is able to reach high idle speed. Refer to Troubleshooting, "Speed Control - Test" for the proper troubleshooting procedure.

Electrical Connectors

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

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.

2. 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.
   Show/hide table

   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.

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

Air Inlet and Exhaust System

1. Observe the indicator lamps. Check for an air filter restriction indicator. Clean plugged air filters or replace plugged air filters. Refer to the Operation and Maintenance Manual for additional information.

2. Check the air inlet and exhaust system for restrictions and/or for 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 following parameters from Cat ET:

• 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.

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

3. 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, "Air in Fuel - Test" for more information.

   Show/hide table

   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.

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

5. 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".

6. 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.