Swapping the Engine on a JLG 40HA Boom Lift

[MikePhua]

Why Replace the Ford VSG-411
The JLG 40HA articulating boom lift, widely used in construction and maintenance, was originally equipped with the Ford VSG-411 gasoline engine. While this engine served reliably for years, many units have reached the end of their service life. Operators now seek alternatives—especially diesel options—for better fuel efficiency, torque, and longevity. Diesel engines also offer improved performance in cold climates and lower fire risk in industrial settings.
Challenges of an Engine Swap
Replacing the VSG-411 with a diesel engine is technically feasible but involves significant mechanical and electrical modifications. The original engine is integrated with the hydraulic pump drive, control wiring, and boom safety systems. A successful swap requires:

• Bellhousing plate and flex plate compatible with the new engine
  
• Pump coupling to match the hydraulic system
  
• Custom motor mounts for physical alignment
  
• Fuel system conversion from gasoline to diesel
  
• Exhaust routing and muffler adaptation
  
• Electrical rewiring to integrate sensors and ignition logic
  
• Boom harness updates to maintain safety interlocks
  

These components are not sold as a kit by JLG, and sourcing them individually can cost upwards of $9,000–$10,000 USD depending on engine choice and labor.
Diesel Engine Options and Fitment
Popular diesel candidates include:

• Kubota V2203 or D1703: Compact, reliable, and widely available in industrial configurations
  
• Yanmar 3TNV series: Lightweight and efficient, often found in light towers and generators
  
• Deutz D2.9 or D2011: Known for durability and modular design
  
• Cummins B3.3 or QSF2.8: Higher torque, but may require more space and cooling
  

When selecting an engine, prioritize industrial variants over automotive types. Industrial engines offer better compatibility with hydraulic drives and simplified wiring. A machinist may be needed to fabricate custom brackets or modify the bellhousing.
Legal and Safety Considerations
If the machine is used commercially or on job sites with employees, safety compliance becomes critical. Any modification to the powertrain may void manufacturer certifications and expose the owner to liability. In the event of an accident, investigators may scrutinize the engine swap and question whether it contributed to the failure.
To mitigate risk:

• Document all modifications and parts used
  
• Ensure the new engine meets or exceeds original performance specs
  
• Retain or replicate all safety interlocks and boom control logic
  
• Consult with an authorized JLG dealer or certified technician
  

Cost Breakdown and Practical Advice
Estimated costs for a diesel swap:

• Used diesel engine: $3,000–$5,000
  
• Bellhousing and flex plate: $800–$1,200
  
• Fuel system components: $300
  
• Exhaust and mounts: $500
  
• Wiring and labor: $2,000–$3,000
  

Total: $6,600–$10,000 depending on parts and labor
One technician in Alberta successfully installed a Yanmar diesel from a retired light tower, fabricating mounts and adapting the pump drive. The machine ran smoother and consumed 30% less fuel, but required two weeks of downtime and careful wiring integration.
Conclusion
Swapping the engine on a JLG 40HA from a Ford VSG-411 to a diesel unit is a rewarding but complex undertaking. It demands mechanical skill, electrical knowledge, and attention to safety compliance. For personal use, the benefits may outweigh the costs. For commercial applications, thorough documentation and professional oversight are essential to ensure reliability and legal protection.