3516B Engine for 994F and 994H Wheel Loaders 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

• Combustion

Recommended 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

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.

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 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 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.

5. 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.

6. 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 Troubleshooting, "Ether Starting Aid - Test".

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

3. 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

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.

2. 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.

Unit Injectors

Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM. Refer to Troubleshooting, "Injector Solenoid - Test" for additional information.

Combustion

Check for mechanical problems in the combustion system.