COUPLING AS- 3078262 - Caterpillar

Probable Causes
Diagnostic codes
Event codes
Fuel supply
Electrical power supply to the Electronic Control Module (ECM)
Starting aids (if applicable)
Engine shutdown switches (if applicable)
Engine speed/timing
Unit injectors
CombustionRecommended Actions
Diagnostic Codes, Event Codes, and Electrical Power Supply to the ECM
Certain diagnostic codes and/or event codes may prevent the engine from starting. Connect Caterpillar Electronic Technician (ET) and check for active codes and/or for logged codes. Troubleshoot any codes that are present before continuing with this procedure.Note: If Cat ET will not communicate with the ECM, the problem is most likely with the electrical power supply to the ECM. Refer to Troubleshooting, "Electrical Power Supply - Test".Fuel Supply
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.
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 which may block the fuel supply.
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.
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 injectorsNote: 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.
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 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)
If cold ambient conditions exist, check operation of starting aids. Verify that the ether system is operating correctly. Refer to Troubleshooting, "Starting Aid - Test".
Ensure the proper operation of the jacket water heater. Repair the jacket water heater and/or replace the jacket water heater, if necessary.
Check for presence of solidified fuel (wax). Engine Shutdown Switches (if applicable)
The engine shutdown switches should be in the OFF position. Use Cat 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.Engine Speed/Timing
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.
Ensure that the timing