The Engine Crankshaft Turns Too Slowly
Probable Causes
- Low battery voltage
- Faulty cable or connection (battery to starting motor)
- Incorrect lubrication oil
- Faulty starting motor
- Extra load
- Internal mechanical problem
Recommended Repairs
Low Battery Voltage
Check battery voltage. If the battery voltage is less than 12 volts for a 12 volt system, or 24 volts for a 24 volt system, put a charge on the battery. If the battery will not keep a charge, load test the battery. Refer to Systems Operation, Testing And Adjusting, "Electrical System" and Special Instruction, SEHS7633, "Battery Test Procedure".
Faulty Cable or Connection
With the ignition switch in the "START" position, check the voltage at the connection of the battery cable to the starting motor. If there is no voltage, or if the voltage is low at this connection and there is good voltage at the battery, check for a faulty battery cable. Also check all connections between the battery and the starting motor.
Incorrect Lubrication Oil
Ensure that the proper lubrication oil is installed. Use the recommended lubrication viscosities that are listed in the Operation And Maintenance Manual.
Faulty Starting Motor
Remove the starting motor and test the starting motor. Repair the starting motor or install a new starting motor.
Extra Load
Check the driveline for free movement. Disconnect the PTO drives or remove the PTO drives, if equipped. Remove engine accessories and inspect engine accessories that put an additional load on the engine. The following components should be inspected:
- Air compressor
- Power steering pump
- Engine oil pump
- Hydraulic oil pump
Internal Mechanical Problem
If the engine cranks too slowly and the driven equipment has been disconnected, the engine must be disassembled. After the engine is disassembled, inspect the engine for other internal problems. Possible internal problems include the following conditions:
- Damaged internal parts
- Binding in the valve mechanism
- Bearing seizure
- Piston seizure
- Valve and piston contact
The Engine Crankshaft Turns Freely
Note: Use the following information as a guide to help solve a hard starting problem when the engine runs properly after starting.
Probable Causes
- Low fuel level
- Low quality fuel
- Fuel waxing
- Air in fuel or no fuel
- Low fuel pressure
- Improper starting procedure
- Faulty fuel shutoff solenoid
- Incorrect fuel Setting
- Incorrect fuel injection timing
- Faulty fuel injector nozzles
- Faulty fuel ratio control
- Faulty fuel injection pump
- Improper camshaft timing
- Low cylinder compression
Recommended Repairs
Low Fuel Level
Visually check the fuel level. Do not rely on the fuel gauge. The lack of exhaust smoke or the lack of intermittent firing during cranking typically indicates insufficient fuel.
Low Quality Fuel
Check for water in the fuel. If water is in the fuel, drain the tank and refill with a good quality diesel fuel. Refer to Supplement, SEBU6385, "Caterpillar On-Highway Diesel Truck Engine Fluids Recommendations" for more information.
Fuel Waxing
For cold outside temperatures, check for the presence of fuel waxing. Refer to Troubleshooting, "Fuel Quality" for details. Check for proper operation of ether starting system and/or air inlet heater (if equipped).
Air in Fuel or No Fuel
Refer to Troubleshooting, "Air In Fuel". If fuel is not present in the sight gauge in the return line, refer to Systems Operation, Testing and Adjusting, "3406C Diesel Truck Engine".
Low Fuel Pressure
Replace the primary fuel filter and the secondary fuel filter. Check the fuel lines for blockage or damage. If this is not the cause, check the fuel transfer pump. Repair the fuel transfer pump or install a new fuel transfer pump. Refer to Systems Operation, Testing and Adjusting, "3406C Diesel Truck Engine".
Improper Starting Procedure
Refer to the Operation And Maintenance Manual, "3406C Diesel Truck Engine" for the correct starting procedure and cold weather recommendations.
Faulty Fuel Shutoff Solenoid
The Fuel Shutoff Solenoid should produce a click as the keyswitch is first turned to the "ON" position. If the solenoid is not heard, check for battery voltage across the solenoid terminals while the keyswitch is "ON". If voltage is not present, troubleshoot the electrical system. If voltage is present, temporarily remove the solenoid. Verify that the solenoid plunger retracts when the keyswitch is turned to the "ON" position.
Incorrect Fuel Setting
The fuel setting procedure can be performed with the governor and fuel injection pump on the engine. Refer to System Operation, Testing and Adjusting, "3406C Diesel Truck Engine" for the correct procedure.
Incorrect Fuel Injection Timing
Check fuel injection timing. Refer to Systems Operation, Testing And Adjusting, "3406C Diesel Truck Engine" for details.
Faulty Fuel Injector Nozzles
The fuel injection nozzles are not serviced. Remove the injectors from the engine and refer to System Operation, Testing and Adjusting, "3406C Diesel Truck Engine" for the proper testing procedure. Replace the fuel injector nozzles, as needed.
Faulty Fuel Ratio Control
The fuel ratio control uses oil pressure to restrict the rate of rack movement. When the engine is stopped, the fuel ratio control will extend to the full fuel position for easier starts. The fuel ratio control adjustment can be found in Systems Operation, Testing and Adjusting, "3406C Diesel Truck Engine".
Faulty Fuel Injection Pump
Test the fuel injection pump. Refer to the Tool Operating Manual, "Install and Test Fuel Injection Pumps Used on 3406B, 3406C, and 3406 PEEC Engines Using the 4C8192 Heavy-Duty Coupling on Fiets" for the test procedure.
Improper Camshaft Timing
The front cover assembly must be removed in order to inspect the timing gears. Refer to Disassembly and Assembly, "3406C Truck Engine" for the proper procedure.
Low Cylinder Compression
Check for signs of broken piston rings, faulty cylinder head gasket, and worn cylinders. Check the inlet valves and the exhaust valves for signs of leakage. If the engine runs properly after starting and there is not excessive blowby or excessive oil consumption, the cylinder compression is probably acceptable.