Troubleshooting Start-Then-Stall Issues in the 1995 SkyTrak 8042 Telehandler

[MikePhua]

The Role of the SkyTrak 8042 in Construction History
The SkyTrak 8042, introduced in the early 1990s, was part of a wave of telehandlers that revolutionized material handling on construction sites. Manufactured by SkyTrak, a brand that later became part of JLG Industries (founded in 1969), the 8042 was designed to lift heavy loads to heights of over 40 feet with precision and stability. Its popularity stemmed from its rugged design, four-wheel drive capability, and straightforward mechanical systems that made it a favorite among contractors and rental fleets.
By the mid-1990s, SkyTrak had sold thousands of units across North America, with the 8042 becoming a staple in framing, masonry, and roofing operations. Its boom reach, load chart flexibility, and operator visibility made it ideal for both urban and rural job sites.
Start-Then-Stall Behavior and Common Causes
When a 1995 SkyTrak 8042 starts and then immediately dies, the issue typically lies in one of three systems:

• Fuel Delivery System: A weak or failing lift pump may not maintain adequate fuel pressure after initial ignition. If the injection pump receives insufficient fuel, combustion ceases within seconds.
  
• Fuel Solenoid Function: The fuel shutoff solenoid controls the flow of diesel to the injection pump. If the solenoid is faulty, miswired, or receiving intermittent voltage, it may close prematurely, cutting off fuel.
  
• Electrical Supply and Safety Interlocks: Older SkyTrak models include safety switches tied to seat position, parking brake, and boom angle. A malfunctioning switch or corroded connector can interrupt the ignition circuit or fuel solenoid power.
  

In one documented case, a technician replaced both the lift pump and solenoid, yet the machine continued to stall. The root cause turned out to be a frayed wire near the ignition switch that intermittently dropped voltage to the solenoid coil. Once repaired, the machine ran reliably.
Understanding the Fuel Solenoid and Its Wiring
The fuel solenoid on the 8042 is typically a two-stage unit:

• Pull-in Coil: Engages during startup to open the fuel valve
  
• Hold-in Coil: Maintains the valve position once the engine is running
  

These coils are wired through the ignition switch and sometimes routed through a relay. If the hold-in coil fails or loses voltage, the solenoid retracts and shuts off fuel. Technicians should:

• Test voltage at the solenoid during cranking and after startup
  
• Inspect ground connections and relay terminals
  
• Check for corrosion or loose pins in the wiring harness
  

Using a multimeter and a test light can help isolate voltage drops or intermittent faults. In some cases, bypassing the solenoid temporarily with a fused jumper wire can confirm diagnosis.
Pump Replacement and Fuel System Integrity
Replacing the lift pump is a common first step, especially if the machine has sat idle for extended periods. Mechanical lift pumps can lose prime or suffer diaphragm failure. When installing a new pump:

• Ensure all fuel lines are free of air and leaks
  
• Bleed the system at the injection pump inlet
  
• Replace fuel filters and inspect the tank for sediment
  

A clogged fuel filter can mimic pump failure by restricting flow. In older machines, algae growth in diesel tanks is also a concern, especially in humid climates. Biocide additives and tank cleaning may be necessary.
SkyTrak’s Evolution and Market Impact
SkyTrak was acquired by JLG Industries in 2003, bringing its telehandler expertise into a broader portfolio of aerial work platforms. The 8042 model continued production into the early 2000s before being updated with newer engines and electronic controls. Despite its age, the 1995 version remains in use across North America, particularly in rural construction and agricultural settings.
JLG, headquartered in Pennsylvania, has produced over 100,000 telehandlers under various brands, with SkyTrak models accounting for a significant portion of that volume. The 8042’s legacy lies in its simplicity and reliability—traits that make it a favorite among mechanics who prefer mechanical diagnostics over electronic troubleshooting.
Recommendations for Long-Term Reliability
To keep a 1995 SkyTrak 8042 running smoothly:

• Inspect and clean all electrical connections annually
  
• Replace fuel filters every 250 hours or sooner in dusty environments
  
• Test solenoid function with direct voltage before replacing
  
• Keep a wiring diagram on hand for tracing ignition and fuel circuits
  
• Use high-quality diesel and additives to prevent microbial growth
  

For machines used seasonally, draining the fuel tank and disconnecting the battery during storage can prevent many startup issues.
Conclusion
The start-then-stall issue in the 1995 SkyTrak 8042 is often solvable with methodical diagnostics and attention to fuel and electrical systems. While newer telehandlers rely on electronic control modules and CAN bus diagnostics, the 8042 remains a mechanical workhorse. Its continued service across job sites is a testament to its design—and to the operators and technicians who keep it alive with skill and persistence.