3512C Engine and 785D Off-Highway Truck/Tractors Caterpillar

Probable Causes

• Diagnostic codes

• Event codes

• Electrical connectors

• Switches

• Circuit breakers

• Fuel supply

Recommended Actions

Diagnostic Codes and/or Event Codes

Certain diagnostic codes and/or event codes may cause an engine shutdown. Connect Caterpillar Electronic Technician (ET) and check for active codes and for logged codes. Troubleshoot any codes that are present prior to continuing with this procedure.

Electrical Connectors

1. Check for correct installation of the J1/P1 and J2/P2 connectors for the Electronic Control Module (ECM). Also, thoroughly inspect the connectors for the engine speed/timing sensors. Refer to Troubleshooting, "Electrical Connectors - Inspect".

2. Inspect the battery wires from the ECM to the battery compartment. Refer to the Schematic for specific wiring information. Check the keyswitch input to the ECM. Check the unit injector connectors and associated wiring for damage, or for intermittent problems. Inspect the wires and connectors to all circuit protection for the engine. Check the power and ground connections to the ECM. Check any engine shutdown switches and associated wiring. Refer to Troubleshooting, "Electrical Power Supply - Test".

Switches

Check any engine shutdown switches and associated wiring. If the application is equipped with an overspeed verify switch, check the switch for correct operation. If equipped, verify that the crank without injection plug is installed securely.

Circuit Breakers

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.

Fuel Supply

1. Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only. If necessary, add fuel to the fuel tank. If the engine has been run out of fuel, it will be necessary to prime the fuel system. Refer to the Operation and Maintenance Manual.

2. 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.

3. Check the fuel tank for debris or foreign objects which may block the fuel supply.
   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. 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: Check the fuel system for air.

5. Check fuel quality. Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual.

6. Check the filtered fuel pressure while the engine is being cranked. Refer to Systems Operation/Testing and Adjusting.

   If the fuel pressure is low, replace the fuel filters. Clean the primary filter/water separator of debris. Refer to the Operation and Maintenance Manual.

   If the fuel pressure is still low, check the operation of the fuel pressure regulating valve. Also, check for the proper operation of the fuel transfer pump. Refer to Systems Operation/Testing and Adjusting.