3176C, 3406E and 3456 Industrial Engines Troubleshooting – Engine Stalls at Low RPM

Probable Causes


  • Diagnostic codes 
  • Fuel supply 
  • Air supply 
  • Engine idle 
  • Accessory equipment 
  • Unit injectors 

Recommended Actions

Diagnostic Codes

Check for active diagnostic codes on Caterpillar Electronic Technician (ET). Troubleshoot any active codes before continuing with this procedure.

Fuel Supply


  1. 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 the Operation and Maintenance Manual.


  1. Ensure that the fuel supply valve (if equipped) is in the full OPEN position.


  1. 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.


  1. 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 injectors 

    Note: A sight glass in the low pressure supply line is helpful in diagnosing air in the fuel.


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


  1. Check the fuel filters.


  1. Check the diesel fuel for contamination. Refer to Systems Operation/Testing and Adjusting.


  1. 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.

Air Supply

Check for restrictions in the air inlet system. Refer to Systems Operation/Testing and Adjusting.

Verify that the air shutoff valves are open.

Engine Idle

Check the parameter for the low engine idle (if applicable). Refer to Troubleshooting, “Configuration Parameters”.

Accessory Equipment

Check all accessory equipment for problems that may create excessive load on the engine. Repair any damaged components or replace any damaged components.

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 Electronic Control Module (ECM).


  1. Perform the “Cylinder Cutout Test” on Cat ET in order to identify any injectors that might be misfiring.


  1. If Cat ET indicates a problem, remove the electronic unit injector from the suspect cylinder and install a new electronic unit injector. Refer to Disassembly and Assembly.


  1. Ensure that the repairs have eliminated the problem. If there is still a problem, refer to Troubleshooting, “Injector Solenoid – Test”.


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