Intermittent No-Start Condition on the Case 590 Super L Backhoe

[MikePhua]

The Super L Series and Its Mechanical Simplicity
The Case 590 Super L was introduced in the late 1990s as part of Case Construction’s flagship backhoe loader lineup. Built for heavy-duty excavation, trenching, and material handling, the Super L featured a turbocharged Cummins 4BT engine, mechanical fuel injection, and a straightforward electrical system. With an operating weight of over 15,000 lbs and breakout forces exceeding 11,000 lbs, it became a favorite among municipalities and contractors for its power-to-size ratio and ease of service.
Case Corporation, founded in 1842 and later merged into CNH Industrial, has long emphasized mechanical reliability and operator-friendly design. The Super L series was produced during a transitional era—before electronic engine control units became standard—making it ideal for field repairs and diagnostics without specialized tools.
Terminology Annotation
- Fuel Shutoff Solenoid: An electrically actuated valve that controls fuel flow to the injection pump. It engages when the ignition is turned on and disengages to stop the engine.
- Cranking: The rotation of the engine by the starter motor, typically without combustion if fuel or ignition is absent.
- Heat-Related Failure: A condition where electrical components malfunction due to elevated temperatures, often after prolonged operation.
- Test Light: A diagnostic tool used to verify voltage presence at a circuit or component.
Symptoms of the No-Start Condition
Operators have reported that the 590 Super L starts reliably when cold but fails to fire after extended operation. The engine cranks normally, but combustion does not occur. After sitting for a period, the machine starts again without issue. When running, performance is unaffected—no loss of power, misfiring, or stalling.
This pattern suggests a heat-sensitive failure, most likely in the fuel delivery system. The most common culprit is the fuel shutoff solenoid, which may lose functionality when exposed to engine heat, preventing fuel from reaching the injectors during restart.
A Story from the Field
In Arkansas, a contractor using a 590 Super L for septic trenching noticed the machine refused to start after a lunch break. The engine cranked strongly, but wouldn’t fire. After waiting 45 minutes, it started without hesitation. Suspecting a fuel issue, he checked the solenoid mounted on the injection pump. Using a test light, he confirmed that voltage was present during cranking. However, the solenoid failed to actuate. Replacing the solenoid resolved the issue permanently.
Diagnostic Strategy and Repair Recommendations
To diagnose a no-start condition:

• Confirm that the engine cranks with normal speed and sound
  
• Check for voltage at the fuel shutoff solenoid during ignition and cranking
  
• Listen for the solenoid click when the key is turned on
  
• If voltage is present but the solenoid does not actuate, replace it
  
• If no voltage is present, inspect the ignition switch, relay, and wiring harness
  

For solenoid replacement:

• Disconnect the battery before servicing
  
• Remove the solenoid from the injection pump carefully to avoid damaging threads
  
• Install the new solenoid and torque to spec
  
• Reconnect wiring and test for proper engagement
  

Some operators choose to bypass the solenoid temporarily by manually actuating the fuel lever, but this should only be done for diagnostic purposes and not as a long-term solution.
Preventative Maintenance and Best Practices
To prevent future no-start issues:

• Inspect solenoid terminals quarterly for corrosion or loose connections
  
• Replace solenoids every 2,000 hours or as part of major service intervals
  
• Use dielectric grease on connectors to prevent moisture intrusion
  
• Keep wiring harnesses secured and away from heat sources
  
• Monitor restart behavior and log any intermittent failures
  

For machines operating in hot climates or under continuous load, consider installing a heat shield or relocating the solenoid to reduce thermal exposure.
Industry Trends and Legacy Support
As of 2025, CNH Industrial continues to support legacy Case models through its dealer network and online parts portals. Aftermarket suppliers offer replacement solenoids, wiring kits, and diagnostic tools compatible with the Super L series. Some technicians retrofit upgraded solenoids with higher thermal tolerance and improved sealing.
Meanwhile, newer backhoe loaders feature electronic engine control and integrated diagnostics, but many operators still prefer the mechanical transparency of the Super L. Its ability to be serviced in the field without laptops or proprietary software makes it a valuable asset in remote or rugged environments.
Conclusion
The Case 590 Super L’s intermittent no-start condition is often caused by a heat-sensitive failure of the fuel shutoff solenoid. With a simple diagnostic approach and proper replacement, the issue can be resolved quickly. For operators and technicians, understanding the interaction between electrical and fuel systems is key to maintaining uptime and avoiding unnecessary shop visits. This classic backhoe continues to prove its worth—especially when its systems are kept clean, cool, and connected.