Troubleshooting Starting Issues in the Case 60XT Skid Steer: Fuel System, Solenoids, and Bleeding Techniques

[MikePhua]

Overview of the Case 60XT and Its Engine Platform
The Case 60XT skid steer loader is a mid-sized compact machine powered by the Cummins 4-390 diesel engine—a naturally aspirated 4-cylinder known for its reliability and simplicity. Despite its rugged design, starting issues can arise due to fuel delivery problems, electrical faults, or air intrusion in the injection system. Diagnosing these problems requires a methodical approach, especially when symptoms mimic electrical failure but stem from fuel system irregularities.
Initial Symptoms and Observations
Operators have reported the following behavior:

• Engine ran normally, then suddenly shut off as if the key was turned off.
  
• A broken wire to the fuel solenoid was discovered and repaired.
  
• After repair, the engine restarted but later quit again.
  
• Fuel solenoid audibly clicks when the key is turned on.
  
• A second solenoid below the first, connected to a temperature sensor, appeared inactive when tested with voltage.
  

These symptoms suggest a combination of electrical and fuel system issues, possibly compounded by air in the lines.
Understanding the Fuel Solenoid and Thermo Wax Motor
The Case 60XT uses two key components on the injection pump:

• Fuel Shutoff Solenoid
  Located on top of the pump, this solenoid controls fuel flow to the injectors. A clicking sound indicates activation, but internal sticking or partial movement can still prevent fuel delivery.
  
• Thermo Wax Motor
  Mounted below the solenoid, this temperature-sensitive actuator gradually adjusts fuel delivery based on engine temperature. It does not respond instantly to voltage and requires several minutes to activate.
  Important note: This component does not affect starting or shutdown unless wires are misrouted.
  

Terminology Explained

• Fuel Solenoid: An electrically controlled valve that opens or closes fuel flow to the injection system.
  
• Thermo Wax Motor: A temperature-based actuator that expands wax internally to move a plunger, adjusting fuel delivery over time.
  
• Bleeding Injectors: A process of releasing trapped air from fuel lines to ensure proper injection and combustion.
  

Common Misdiagnoses and Clarifications

• Hearing the solenoid click does not guarantee full movement. Internal sticking can prevent fuel flow even if the coil energizes.
  
• Fuel flow at the filter bleed screw may appear normal but can include air bubbles, misleading inexperienced technicians.
  
• The presence of fuel at the pump does not confirm delivery to the injectors—airlocks can still prevent combustion.
  

Field Anecdote: Bleeding the Injectors for a Successful Start
In Kentucky, an operator followed standard troubleshooting steps after his 60XT quit unexpectedly. After repairing a broken wire and replacing the fuel filter and water separator, he still faced starting issues. Upon loosening the injector line nuts and cranking the engine, he observed dry lines followed by a strong spray of fuel. Once tightened, the engine started immediately and ran smoothly—confirming that air in the lines was the root cause.
Recommended Diagnostic and Repair Steps

1. Inspect Electrical Connections
   • Check for broken or corroded wires at the fuel solenoid and temperature sensor.
     
   • Confirm voltage delivery with a multimeter when the key is turned on.
     
2. Test Fuel Solenoid Movement
   • Remove the solenoid and manually inspect plunger movement.
     
   • Clean or replace if sticking is observed.
     
3. Bleed the Fuel System
   • Fill the fuel filter manually before installation.
     
   • Open the bleed screw and crank the engine until fuel flows steadily.
     
   • Loosen injector line nuts 1–2 turns and crank until fuel sprays from each.
     
   • Retighten and start the engine with throttle at half position.
     
4. Inspect for Air Intrusion
   • Check all fuel lines and fittings for leaks.
     
   • Replace any cracked hoses or loose clamps.
     
5. Evaluate Lift Pump Performance
   

• A weak or failing lift pump can cause intermittent fuel delivery.
  
• Replace if fuel pressure is inconsistent or low.
  

Additional Observations and Mechanical Notes

• A broken bolt near the throttle or shutoff linkage may affect fine adjustments.
  
• Inspect for missing components or signs of impact near adjustment screws.
  
• Ensure all mechanical linkages are intact and properly aligned.
  

Preventive Maintenance Tips

• Replace fuel filters every 250–500 hours.
  
• Use clean diesel and drain water separators regularly.
  
• Periodically test solenoids and wax motors for proper function.
  
• Keep electrical connections dry and protected from vibration.
  

Conclusion: A Systematic Approach to Reliable Starts
Starting problems in the Case 60XT often stem from a combination of electrical faults and fuel system airlocks. While solenoids and sensors play a role, the most common culprit is air trapped in the injector lines after filter changes or fuel interruptions. By methodically inspecting components, bleeding the system, and verifying solenoid movement, operators can restore reliable performance and avoid unnecessary downtime. With a bit of patience and mechanical intuition, even stubborn starting issues can be resolved efficiently.