3176C, 3196 and 3406E Engines for 725, 730, 735, 740, and 740 Ejector Articulated Trucks Caterpillar

Probable Causes

• Active engine derate

• Electrical connectors

• Fuel supply

Recommended Repairs

Active Engine Derate

Use ET to check for any active derates or any logged derates. ET will display a status indicator if a derate is active. The engine may be derated due to one of the following conditions: high altitude, dirty air filters and other factors.

Electrical Connectors

1. Use ET to check for the following logged diagnostic codes: 168-01 "System Voltage Low" and 168-02 "System Voltage intermittent". If either of these diagnostic codes are logged, proceed to Troubleshooting, "Electrical Power Supply".

2. Inspect the battery wires from the ECM back to the battery compartment. Refer to the Electrical System Schematic. Inspect the wires and the power relay. Check the power and ground connections to the ECM. Refer to Troubleshooting, "Electrical Power Supply Circuit - Test" for more information.

Fuel Supply

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.

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

3. Check for air in the low pressure 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 low pressure supply line is helpful in diagnosing air in the fuel. Refer to Testing and Adjusting for more information.

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. Purge air from the low pressure fuel supply circuit. Refer to Operation and Maintenance Manual, "Fuel System - Prime" for the correct procedure.

5. Check fuel quality. In temperatures below 0 °C (32 °F), check for solidified fuel (wax). Refer to Special Instruction, SEBD0717, "Diesel Fuels And Your Engine".

6. Check the fuel pressure during engine cranking. Check the fuel pressure after the fuel filter. Refer to Testing and Adjusting for the correct pressure values. 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.