Identifying and Maintaining the Engine in the JLG 40H Boom Lift

[MikePhua]

JLG’s 40H and Its Role in Aerial Access
The JLG 40H boom lift was introduced during the late 1980s and remained in production into the 1990s, serving as a reliable mid-range telescopic lift for construction, maintenance, and industrial access. With a platform height of 40 feet and a horizontal outreach of over 30 feet, the 40H offered a balance of reach and maneuverability. It was available in both 2WD and 4WD configurations, and its popularity stemmed from its simplicity, mechanical durability, and ease of service.
JLG Industries, founded in 1969, quickly became a leader in aerial work platforms. By the time the 40H was released, the company had already established a reputation for rugged machines that could operate in harsh environments with minimal downtime. The 40H was often powered by Ford industrial engines, which were widely used across multiple equipment platforms due to their reliability and parts availability.
Terminology Notes

• Boom Lift: A type of aerial work platform with a telescoping arm for vertical and horizontal access.
  
• Industrial Engine: An engine adapted for use in equipment rather than vehicles, often with simplified electronics and heavy-duty components.
  
• LSG/LRG Series: Ford’s industrial engine family, including the 423, 425, and earlier 411/413 variants.
  
• Carbureted vs. Fuel Injected: Two methods of fuel delivery; carburetors mix fuel mechanically, while injection systems use pressurized delivery.
  
• Valve Cover Identification: A visual method for identifying engine series based on the shape and bolt pattern of the valve cover.
  

Engine Identification Challenges and Clues
The JLG 40H was typically equipped with Ford industrial engines from the LSG or LRG series. These included:

• LSG423: A 2.3L inline-four, carbureted
  
• LRG425: A 2.5L inline-four, fuel-injected
  
• LSG/LRG411 and 413: Earlier versions with smaller displacement
  

Identification can be tricky due to overlapping features and the lack of consistent labeling on older machines. Key clues include:

• Valve cover shape and bolt layout
  
• Intake manifold design (carburetor vs. throttle body)
  
• Distributor location and style
  
• Engine block casting numbers
  
• Emissions label (if still intact)
  

In one equipment yard in Nevada, a technician identified a 425 engine in a 40H by comparing the valve cover to a known LRG425 used in a propane-powered floor scrubber. The match was confirmed by block casting numbers and intake configuration.
Historical Context and Engine Origins
The LSG and LRG engines were derived from British Ford designs used in vehicles like the Cortina and Pinto during the 1960s and 1970s. These engines were adapted for industrial use with hardened valve seats, simplified wiring, and compatibility with LPG or gasoline. Their longevity and parts availability made them a favorite among equipment manufacturers.
In one restoration project in Pennsylvania, a mechanic rebuilt a 423 engine using parts sourced from a vintage Ford Capri. The cylinder head, pistons, and timing components matched perfectly, highlighting the cross-compatibility between automotive and industrial variants.
Maintenance and Performance Considerations
To keep the engine running smoothly:

• Change oil every 100–150 hours using SAE 10W-30
  
• Replace air and fuel filters every 250 hours
  
• Inspect spark plugs and ignition wires quarterly
  
• Clean carburetor or throttle body annually
  
• Check valve lash and timing every 500 hours
  

Recommended upgrades:

• Install electronic ignition for better cold starts
  
• Use high-quality fuel stabilizer in seasonal climates
  
• Replace mechanical fuel pump with electric for consistent delivery
  
• Add inline fuel filter to protect carburetor or injectors
  

In one fleet in Texas, switching to synthetic oil and upgrading to an electronic ignition module reduced misfires and improved fuel economy during summer operations.
Parts Sourcing and Engine Support
Despite their age, LSG and LRG engines are still supported by aftermarket suppliers. Common parts include:

• Gaskets and seal kits
  
• Carburetor rebuild kits
  
• Ignition modules and coils
  
• Water pumps and thermostats
  
• Valve cover gaskets and timing belts
  

For hard-to-find components, cross-referencing with automotive equivalents often yields results. In one case in Ontario, a technician replaced a cracked intake manifold using a part from a 1974 Ford Pinto, saving weeks of downtime.
Final Thoughts
The JLG 40H boom lift remains a dependable machine, and its Ford industrial engine—whether a 423, 425, or earlier variant—continues to serve with resilience. Identifying the exact engine may require detective work, but once confirmed, maintenance and parts support are readily available. In the rhythm of aerial access, the engine isn’t just a power source—it’s the heartbeat of elevation. And with the right care, it keeps lifting long after the manuals fade.