F438066 Force BY-PASS VALVE COVER

Probable Causes
Diagnostic codes
Event codes
Electrical connections
Unit injector connectors
Fuel supply
Engine shutdown switch (if applicable)Note: If the problem only occurs under certain conditions such as full load or engine operating temperature, then perform the test under those operating conditions.Recommended Actions
Diagnostic Codes or Event Codes
Certain diagnostic codes or event codes may cause the engine to shutdown. Connect the Caterpillar Electronic Technician (ET) and check for active codes and/or logged codes. Troubleshoot any codes that are present before continuing with this procedure.Electrical Connections
Inspect the wiring from the Electronic Control Module (ECM) to the breaker panel. Refer to the Schematic for the engine. Inspect any device that has been installed for circuit protection. Ensure that battery power is present at the ECM. Ensure that the ground circuits are providing electrical continuity to the ECM. Refer to the diagnostic functional test Troubleshooting, "Electrical Power Supply Circuit - Test".
Check the circuit between the ECM and the keyswitch. Refer to the Schematic for the engine. Also, ensure that all electrical connectors are in good repair. Refer to the diagnostic functional test Troubleshooting, " Electrical Connectors - Inspect".
Check the state of each of the circuit breakers. Reset the circuit breakers if the circuit breakers are tripped. Prior to returning the engine to service, determine the condition that caused the circuit breaker to trip. Make the necessary repairs.
Aftermarket engine protection devices usually interrupt power to the ECM. Check for correct installation and operation of aftermarket engine protection devices. It may be necessary to bypass aftermarket devices in order to continue testing. Unit Injector Connectors
Check the unit injector connectors J300/P300 and associated wiring for damage, or for intermittent problems. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".Fuel Supply
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 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 injectorsRefer to the Operation and Maintenance Manual.Note: A sight glass in the fuel supply line is helpful in diagnosing air in the fuel.
Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual.
Check the fuel pressure during engine cranking. Check the fuel pressure after the fuel filter. Refer to the Systems Operation/Testing and Adjusting. 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. Engine Shutdown Switch (If Applicable)
Use Cat ET to monitor the status of the engine shutdown switches. Check for status indicators that are active due to the engine shutdown switch. Determine the cause for the shutdown and make any repairs necessary.