Converting the Caterpillar D6 9U to Electric Start

[MikePhua]

The Caterpillar D6 9U series, introduced in the late 1940s, is a robust and versatile crawler tractor renowned for its durability and performance in various heavy-duty applications. Originally equipped with a pony motor for starting, many operators have sought to convert these machines to direct electric start systems to enhance reliability and ease of use.
Understanding the Original Starting System
The D6 9U was initially designed with a pony motor, a small auxiliary engine used to start the main diesel engine. This system required manual operation and maintenance, which could be cumbersome and time-consuming. Over the years, as technology advanced and the availability of reliable electric starters increased, the desire to retrofit these machines with electric start systems grew.
Challenges in Conversion
Converting the D6 9U from a pony motor to an electric start involves several technical challenges:

• Compatibility: Ensuring that the new starter motor aligns correctly with the existing engine components.
  
• Mounting: Fabricating or sourcing a suitable bracket to securely mount the starter motor.
  
• Electrical System: Upgrading the electrical system to support the new starter, including wiring and battery capacity.
  
• Cooling System: Modifying or blocking off the existing cooling lines associated with the pony motor.
  

Operators have reported various approaches to these challenges. For instance, some have utilized templates made from file folders to design custom block-off plates for the pony motor exhaust and coolant tubes. These templates are then transferred to steel plates, which are cut and drilled to fit the engine, effectively sealing off the old components and making way for the new starter system.
Selecting the Appropriate Starter Motor
Choosing the right starter motor is crucial for the success of the conversion. The Delco Remy 50MT starter is a popular choice among operators due to its reliability and compatibility with the D6 9U engine. When selecting a starter, consider the following:

• Voltage: The original system was 24 volts, but many conversions opt for a 12-volt system for ease of maintenance and parts availability.
  
• Rotation: Ensure the starter motor's rotation direction matches the engine's requirements.
  
• Power Rating: The starter should have sufficient torque to turn over the diesel engine, especially in cold conditions.
  

Electrical System Upgrades
To accommodate the new starter motor, the electrical system must be upgraded:

• Battery Configuration: For a 12-volt system, two 6-volt batteries are typically wired in series to provide the necessary voltage.
  
• Alternator: The original 6-volt generator may need to be replaced with a 12-volt alternator to ensure adequate charging capacity.
  
• Wiring: All wiring should be inspected and replaced as necessary to handle the increased current demands.
  

Cooling System Modifications
With the removal of the pony motor, modifications to the cooling system are necessary:

• Coolant Lines: Existing coolant lines associated with the pony motor should be blocked off or rerouted to prevent leaks and ensure proper engine cooling.
  
• Air Cleaner Support: The removal of the pony motor may necessitate additional support for the air cleaner assembly to maintain proper airflow.
  

Testing and Troubleshooting
After completing the conversion, thorough testing is essential:

• Starter Operation: Verify that the starter motor engages and turns over the engine smoothly.
  
• Electrical System: Check the charging system to ensure batteries are being properly charged.
  
• Engine Performance: Monitor engine performance to ensure it starts reliably and operates efficiently.
  

Common issues that may arise include starter motor engagement problems, electrical system faults, or engine starting difficulties. Addressing these issues promptly can prevent further complications and ensure the longevity of the conversion.
Conclusion
Converting the Caterpillar D6 9U to an electric start system can significantly enhance its reliability and ease of use. While the conversion presents several challenges, with careful planning and execution, operators can successfully retrofit their machines. By selecting the appropriate starter motor, upgrading the electrical system, and modifying the cooling system, the D6 9U can continue to serve effectively in various heavy-duty applications for years to come.