3176C, 3406E and 3456 Industrial Engines Troubleshooting – Engine Cranks but Does Not Start

Probable Causes


  • Fuel supply 
  • Starting aids (if applicable) 
  • Engine shutdown switches (if applicable) 
  • Diagnostic codes 
  • Event codes 
  • Flash file 
  • Electrical connectors 
  • Engine speed/timing 
  • Air inlet and exhaust system 
  • Combustion 

Recommended Actions

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 prime the fuel system. Refer to Operation and Maintenance Manual for the correct procedure.


  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. Prime the 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 supply line is helpful in diagnosing air in the fuel. Refer to the Systems Operation/Testing and Adjusting manual for more information.


  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.


  1. Check fuel flow after the fuel filters. If the fuel flow is low, replace the fuel filters. If the fuel flow is still low, check the following items: fuel transfer pump, fuel transfer pump coupling and fuel pressure regulating valve.

Starting Aids (if applicable)


  1. If cold ambient conditions exist, check operation of starting aids. Refer to the appropriate starting aid test(s).


  1. Ensure the proper operation of the jacket water heater. Repair the jacket water heater and/or replace the jacket water heater, if necessary.


  1. Check for presence of solidified fuel (wax).

Engine Shutdown Switches (if applicable)

The engine shutdown switches should be in the OFF position. Use Caterpillar Electronic Technician (ET) to verify the status of the shutdown switches. When a shutdown occurs, the keyswitch must be turned to the OFF position for at least 15 seconds before restarting the engine.

Diagnostic Codes or Event Codes

Certain diagnostic codes and/or event codes may prevent the engine from starting. Connect Cat ET and check for active codes and/or for logged codes. Troubleshoot any codes that are present before continuing with this procedure.

Flash File

Verify that the latest flash file has been installed into the Electronic Control Module (ECM).

Electrical Connectors

Disconnect the J1/P1 and J2/P2 ECM connectors. Inspect each connector for moisture and corrosion. Also, inspect the harness and connectors for the unit injectors from the ECM to the valve cover. Inspect the connectors for the engine speed/timing circuit. Refer to Troubleshooting, “Electrical Connectors – Inspect”.

Engine Speed/Timing


  1. Crank the engine and observe the engine speed on the Cat ET status screen. If Cat ET indicates zero rpm, refer to Troubleshooting, “Speed/Timing – Test”.Note: Upon initial cranking, the status for engine speed may indicate that the engine speed signal is abnormal. This message will be replaced with an engine speed once the ECM is able to calculate a speed from the signal.


  1. Ensure that the timing reference gear is installed correctly. The engine will not start if the gear was installed backward. Check for proper orientation between the crankshaft and camshaft drive gears. Correct the orientation and/or replace the drive gear, if necessary. Refer to the Disassembly and Assembly manual.

Air Inlet and Exhaust System


  1. Check the air filter restriction indicator for a plugged filter. If necessary, service the engine. Refer to the Operation and Maintenance Manual.


  1. Check the air inlet and exhaust system for restrictions and/or leaks. Refer to Systems Operation/Testing and Adjusting.


Check for mechanical problems in the combustion system.

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