Troubleshooting JLG 50HT Won't Start

[MikePhua]

The JLG 50HT is a high-reach articulated boom lift commonly used in construction, maintenance, and other heavy-duty tasks that require access to elevated areas. Like all complex machinery, the JLG 50HT can sometimes encounter starting problems, which can lead to downtime on job sites and a range of operational inefficiencies. This article will walk you through common issues and troubleshooting steps that can help address a situation where a JLG 50HT lift won’t start.
Overview of the JLG 50HT
The JLG 50HT is part of the JLG Industries lineup, renowned for producing aerial work platforms, including boom lifts, scissor lifts, and telehandlers. The 50HT model features a 50-foot working height and a horizontal reach of 28 feet. Its versatile articulated boom allows operators to access difficult-to-reach areas, making it a popular choice in construction, maintenance, and event settings.
The machine is powered by either a gas or diesel engine, depending on the configuration. It also has hydraulic systems that control the movement of the boom and other essential components. Because of its complexity and reliance on multiple systems, it’s important to diagnose issues systematically when the equipment fails to start.
Common Causes for a JLG 50HT Not Starting
A variety of issues can cause a JLG 50HT to fail to start. It’s essential to consider all potential factors, including electrical, fuel, and mechanical systems. Below are the most common culprits that could be preventing your lift from starting:
1. Dead or Weak Battery
One of the most common reasons for starting failure is a dead or weak battery. The JLG 50HT requires a powerful battery to crank the engine and supply power to the lift’s electrical systems. Over time, batteries can lose their charge or capacity, especially in cold weather or after long periods of disuse.
Troubleshooting:

• Check Battery Voltage: Use a multimeter to check the battery voltage. A healthy battery typically reads around 12.6 volts when fully charged. If the voltage is below this, the battery may need to be charged or replaced.
  
• Inspect Battery Terminals: Corroded or loose battery terminals can prevent proper contact and inhibit starting. Clean the terminals and ensure they are tightly connected.
  
• Test Battery Condition: If the battery is old or damaged, replacing it with a new one may solve the issue.
  

2. Fuel Supply Issues
Another common cause for starting failure is insufficient or improper fuel delivery. The JLG 50HT relies on either gasoline or diesel, depending on the model. Problems such as empty fuel tanks, clogged fuel filters, or faulty fuel pumps can prevent the engine from starting.
Troubleshooting:

• Check Fuel Tank: Ensure the fuel tank has an adequate supply of fuel. It’s easy to overlook, but an empty tank is a simple problem to solve.
  
• Inspect Fuel Lines: Look for any signs of leaks or blockages in the fuel lines. Blocked fuel lines or a clogged fuel filter can restrict fuel flow to the engine.
  
• Examine the Fuel Pump: A malfunctioning fuel pump can prevent fuel from reaching the engine. If you suspect the fuel pump is the issue, consult a mechanic or technician for further diagnostics.
  

3. Faulty Starter Motor
The starter motor is the component responsible for turning the engine over when you start the machine. If the starter motor is faulty, the engine may fail to start, even if the battery is fully charged and fuel is available.
Troubleshooting:

• Listen for Starter Sounds: When you turn the ignition key, listen for any sounds from the starter. A clicking noise could indicate a faulty solenoid or starter motor. If the starter motor is unresponsive, it may need to be repaired or replaced.
  
• Test the Starter Motor: Use a multimeter to check for voltage at the starter terminal when attempting to start the machine. If there’s no voltage, there may be an issue with the electrical circuit or the starter itself.
  

4. Safety Switches or Interlocks
The JLG 50HT features multiple safety switches and interlocks that prevent the machine from starting if certain conditions are not met. For example, the operator’s platform must be in a safe position, and the parking brake must be engaged before the lift will start. These safety mechanisms are designed to protect the operator and the equipment.
Troubleshooting:

• Check Safety Interlocks: Ensure that all safety features, such as the platform position, parking brake, and control switches, are correctly engaged. Refer to the operator's manual for details on the interlocks for your specific model.
  
• Inspect the Operator’s Platform: If the platform is not in the correct position or is locked, the system may prevent the machine from starting. Verify that the platform is in the proper configuration.
  

5. Electrical System Failure
The electrical system in the JLG 50HT includes numerous components, such as relays, solenoids, fuses, and wiring. Any failure in the electrical system can prevent the machine from starting. This could be due to blown fuses, faulty relays, or damaged wiring.
Troubleshooting:

• Check Fuses and Relays: Inspect all relevant fuses and relays for signs of damage. If a fuse is blown, replace it with one of the correct amperage rating.
  
• Inspect Wiring Connections: Look for any loose, frayed, or damaged wiring. Electrical shorts or open circuits can stop the machine from starting.
  
• Test the Solenoid: The solenoid is responsible for engaging the starter motor. If it is faulty, the engine may not turn over. Test the solenoid and replace it if needed.
  

6. Engine Overheating or Mechanical Issues
In rare cases, the engine may fail to start due to internal mechanical issues or overheating. Overheating could be caused by coolant leaks, a malfunctioning thermostat, or a faulty cooling system.
Troubleshooting:

• Check the Cooling System: Ensure that the engine has sufficient coolant and that the radiator is not clogged. Overheating can cause the engine to seize or malfunction.
  
• Inspect for Leaks: Look for oil or coolant leaks, especially around the engine block and hoses. Leaks can lead to low fluid levels, which can cause starting issues.
  
• Perform a Compression Test: If mechanical failure is suspected, perform a compression test to check the engine’s internal health.
  

When to Call a Professional
While the steps above should help you diagnose and potentially solve common starting issues, some problems may require professional assistance. If you’ve gone through the troubleshooting steps and the JLG 50HT still won’t start, it may be time to consult a qualified mechanic or service technician. They can conduct more advanced diagnostics and perform any necessary repairs, such as replacing the starter motor, fuel pump, or other critical components.
Conclusion
The JLG 50HT is a powerful and versatile machine, but like any complex piece of equipment, it can face starting issues. Common problems include dead batteries, fuel supply issues, faulty starter motors, safety switch malfunctions, electrical system failures, and engine overheating. By following a systematic troubleshooting approach, most issues can be identified and resolved relatively quickly, minimizing downtime.
Regular maintenance, including battery checks, fuel system inspections, and electrical diagnostics, can help prevent many of these issues from occurring in the first place. For more complex problems, calling in a professional technician ensures that the issue is addressed promptly and effectively, helping your JLG 50HT stay operational and reliable on the job site.