Diagnosing Slow Crank Issues on JLG SkyTrak Telehandlers

[MikePhua]

JLG’s SkyTrak Series and Its Role in Material Handling
JLG Industries, founded in 1969 and headquartered in Pennsylvania, has become a global leader in aerial work platforms and telehandlers. The SkyTrak line, introduced in the 1980s, was designed to meet the needs of construction, agriculture, and industrial sectors requiring high-reach material handling with rugged off-road capability. With lifting capacities ranging from 6,000 to 12,000 lbs and boom heights exceeding 50 feet, SkyTrak telehandlers are widely used across North America and beyond.
The SkyTrak series is known for mechanical simplicity, intuitive controls, and field serviceability. However, like many diesel-powered machines, slow cranking during startup can become a recurring issue—especially in older units or those exposed to harsh environments.
Terminology Notes

• Cranking Speed: The rotational speed of the engine during starter engagement, critical for ignition.
  
• Solenoid: An electromechanical switch that controls the flow of current to the starter motor.
  
• Voltage Drop: A reduction in electrical potential across a circuit, often caused by resistance or poor connections.
  
• Cold Start Circuit: A system designed to assist engine ignition in low temperatures, often involving glow plugs or intake heaters.
  

Symptoms and Operational Impact
Slow cranking in a SkyTrak telehandler typically presents as:

• Starter motor turning sluggishly or intermittently
  
• Engine failing to fire despite multiple attempts
  
• Audible clicking from the solenoid without full engagement
  
• Battery draining rapidly during cranking
  
• Reduced productivity due to delayed warm-up cycles
  

In one case, a framing crew in Colorado reported that their SkyTrak 8042 struggled to start each morning. After inspecting the electrical system, they discovered a corroded ground strap between the frame and engine block. Replacing the strap and cleaning the terminals restored full cranking speed.
Field Anecdote and Improvisation
During a warehouse expansion in Ontario, a SkyTrak unit began cranking slowly after sitting idle for two weeks. The operator suspected battery failure, but voltage tested normal. Upon further inspection, the starter solenoid was found to be sticking due to internal moisture. With no replacement on hand, the crew tapped the solenoid housing gently with a rubber mallet while engaging the key. The machine started immediately and continued operating until a new solenoid was installed.
Root Causes and Diagnostic Strategy
Slow cranking can result from multiple factors:

• Weak battery or sulfated cells reducing available amperage
  
• Corroded or loose battery terminals increasing resistance
  
• Faulty starter motor or worn brushes
  
• Sticking solenoid or poor ground connection
  
• Cold weather affecting oil viscosity and starter load
  

To diagnose:

• Measure battery voltage under load; should remain above 10.5V during cranking
  
• Perform a voltage drop test across positive and ground cables
  
• Inspect starter motor for heat damage or brush wear
  
• Test solenoid continuity and engagement response
  
• Check engine oil grade and switch to winter-rated viscosity if needed
  

If the starter motor spins but fails to engage, inspect the flywheel teeth and starter gear alignment. If cranking speed is normal but the engine fails to fire, investigate fuel delivery and glow plug operation.
Preventive Maintenance and Recommendations

• Replace batteries every 3–5 years or when cranking voltage drops
  
• Clean and tighten all cable connections quarterly
  
• Use dielectric grease on terminals to prevent corrosion
  
• Inspect starter motor and solenoid annually
  
• Switch to synthetic oil in cold climates to reduce cranking load
  
• Install block heaters or battery warmers for sub-zero operations
  

For machines stored outdoors, consider using insulated engine covers and scheduling warm-up cycles before shift start.
Design Simplicity and Serviceability
SkyTrak telehandlers are built for field maintenance. The engine bay opens wide, and electrical components are accessible without cab removal. The starter motor and solenoid are mounted in reachable positions, and diagnostic ports allow technicians to monitor system voltage and current draw.
Operators appreciate the machine’s responsiveness and lifting power, but starting reliability is essential for maintaining uptime—especially in seasonal or remote operations.
Conclusion
Slow cranking in JLG SkyTrak telehandlers is often a symptom of electrical resistance, mechanical wear, or environmental stress. With methodical inspection and preventive upgrades, the issue can be resolved and long-term reliability restored. In high-reach material handling, ignition is the first step toward productivity—and the SkyTrak proves that even the strongest lift begins with a dependable start.