JLG 1200 Drives Then Stalls: Troubleshooting and Solutions

[MikePhua]

JLG is a well-known manufacturer of aerial work platforms, including scissor lifts and boom lifts. These machines are commonly used in construction, maintenance, and various industrial applications due to their ability to provide safe access to elevated work areas. One of the most reliable machines in JLG's lineup is the JLG 1200, a telescopic boom lift that can extend up to 120 feet, offering excellent reach and versatility.
However, like all heavy equipment, issues can arise that prevent the machine from operating as intended. One such issue, as reported by some operators, involves the JLG 1200 driving a short distance before stalling. This problem can be frustrating, especially for operators who rely on the machine for complex tasks that require mobility. In this article, we will explore possible causes of the "drives then stalls" issue and suggest solutions to get your JLG 1200 back in operation.
Common Causes of the JLG 1200 Stalling Issue
Several factors can contribute to the issue of the JLG 1200 driving briefly before stalling. Below are the most common causes, along with detailed explanations and possible solutions.
1. Fuel System Problems
One of the most frequent causes of an engine stalling after driving for a short distance is an issue with the fuel system. The fuel system is responsible for delivering the proper amount of fuel to the engine to maintain operation. If any component of the fuel system malfunctions, such as the fuel filter, fuel pump, or fuel injectors, the engine can lose power and stall.

• Fuel Filter: A clogged or dirty fuel filter can prevent the engine from receiving enough fuel. Over time, dirt, debris, and contaminants can build up in the filter, restricting fuel flow.
  Solution: Replace the fuel filter and inspect the fuel lines for any signs of damage or leaks. It's also essential to check for any blockages in the fuel lines that could restrict fuel flow.
  
• Fuel Pump: The fuel pump is responsible for supplying fuel from the tank to the engine. If the pump is faulty or not delivering the correct pressure, it can cause the engine to stall after running for a short period.
  Solution: Test the fuel pump to ensure it is working correctly. If necessary, replace the fuel pump with a new one.
  
• Fuel Injectors: If the fuel injectors are dirty or malfunctioning, they may not be delivering the right amount of fuel to the engine, causing it to stall.
  Solution: Clean or replace the fuel injectors to ensure proper fuel delivery.
  

2. Electrical System Malfunction
The electrical system of the JLG 1200, including the battery, alternator, and wiring, plays a critical role in powering the engine and other components. An issue with the electrical system can lead to a drop in voltage or a loss of power to critical systems, causing the engine to stall.

• Battery: A weak or dead battery may not provide sufficient power to the engine, especially during high-demand periods such as when driving. If the battery is not fully charged or is near the end of its lifespan, it could lead to stalling.
  Solution: Check the battery’s voltage with a multimeter. If the voltage is too low, charge the battery or replace it if necessary.
  
• Alternator: The alternator charges the battery and powers the electrical system while the engine is running. A malfunctioning alternator may not keep the battery charged, causing the engine to stall.
  Solution: Inspect the alternator for any signs of wear or damage. Test the alternator's output and replace it if it is not functioning properly.
  
• Wiring and Fuses: Damaged wiring or blown fuses can disrupt the electrical flow, leading to a loss of power to the engine. This can result in the engine stalling after driving a short distance.
  Solution: Inspect the wiring for any visible damage, fraying, or corrosion. Replace any faulty fuses and repair or replace damaged wiring as needed.
  

3. Hydraulic System Issues
The JLG 1200 utilizes a hydraulic system to power various components, including the drive system and the boom. A malfunction in the hydraulic system can lead to a loss of power and cause the machine to stall, especially when trying to move or lift heavy loads.

• Hydraulic Fluid Level: If the hydraulic fluid level is low, the system may not have enough pressure to operate the drive motors and other components properly, leading to stalling.
  Solution: Check the hydraulic fluid level and top it up if necessary. Also, inspect the hydraulic fluid for signs of contamination or degradation.
  
• Hydraulic Pump: A failing hydraulic pump can result in insufficient pressure to operate the drive system. If the pump is malfunctioning, the machine may drive for a short distance before stalling.
  Solution: Test the hydraulic pump for proper operation. If the pump is not producing enough pressure, it may need to be repaired or replaced.
  

4. Overheating
Overheating is a common issue in any heavy equipment, and the JLG 1200 is no exception. If the engine or hydraulic system overheats, it can lead to a loss of power and cause the machine to stall.

• Engine Overheating: If the engine coolant is low or the cooling system is not functioning properly, the engine can overheat, triggering an automatic shutdown or stalling.
  Solution: Check the coolant level and inspect the radiator, hoses, and thermostat for any signs of damage. Flush the cooling system if necessary and replace any faulty components.
  
• Hydraulic System Overheating: The hydraulic system can also overheat, especially if the fluid is too low or if there is excessive load on the system.
  Solution: Inspect the hydraulic cooler and lines for any blockages or leaks. Ensure the hydraulic fluid is at the correct level and is free from contaminants.
  

5. Transmission or Drive System Issues
Finally, problems with the transmission or drive system of the JLG 1200 can contribute to the stalling issue. If the transmission is not properly engaging or if there is a failure in the drive motor, the machine may stall when trying to move.

• Transmission Fluid: Low or dirty transmission fluid can cause the transmission to malfunction, resulting in stalling after driving a short distance.
  Solution: Check the transmission fluid level and condition. If necessary, replace the fluid and perform a system flush.
  
• Drive Motors: A malfunction in the drive motors can cause the machine to stall, as they are responsible for converting hydraulic power into movement.
  Solution: Inspect the drive motors for any signs of wear or damage. Test the motors for proper operation and replace any faulty components.
  

Conclusion
The issue of a JLG 1200 driving and then stalling can be caused by various factors, ranging from fuel system malfunctions to electrical issues, hydraulic system failures, overheating, or problems with the transmission and drive system. By systematically troubleshooting the machine and addressing each potential cause, operators can identify and resolve the issue to restore the functionality of the machine.
If the problem persists despite troubleshooting, it may be necessary to consult with a JLG technician or service provider for a more thorough diagnosis. Regular maintenance, including fluid checks, electrical system inspections, and hydraulic system upkeep, is essential to prevent such issues from arising in the future and ensure the longevity and reliability of the JLG 1200.