Shutoff Solenoid Troubles on the Case 850K Series 2

[MikePhua]

The Case 850K Series 2 and Its Evolution
The Case 850K Series 2 crawler dozer represents a pivotal point in Case Construction Equipment’s mid-range dozer development. Introduced in the early 2000s, the Series 2 was designed to improve upon the original 850K platform with enhanced electronic controls, refined hydrostatic transmission, and better operator ergonomics. Case, founded in 1842 by Jerome Increase Case, has long been a leader in earthmoving equipment, with the 850 series selling thousands of units globally across construction, forestry, and utility sectors.
The 850K Series 2 features a 6.7-liter turbocharged diesel engine, typically the Case Family IV engine, delivering around 99 net horsepower. With an operating weight of approximately 19,000 pounds and a drawbar pull exceeding 40,000 pounds, the machine is built for grading, clearing, and pushing tasks in demanding terrain. However, like many electronically managed diesel machines, it relies on a fuel shutoff solenoid to control engine shutdown—a component that can become a source of frustration when malfunctioning.
What Is a Shutoff Solenoid
A shutoff solenoid is an electromechanical device that controls the flow of fuel to the injection pump. When energized, it retracts a plunger or rod, allowing fuel to flow. When de-energized, it extends the rod to cut off fuel, stopping the engine. In the Case 850K Series 2, the solenoid is mounted directly on the injection pump, interfacing with the stop lever.
Key terminology:

• Solenoid: A coil of wire that generates a magnetic field when current passes through, used to actuate mechanical movement.
  
• Stop Lever: A mechanical arm on the injection pump that halts fuel delivery when moved.
  
• Continuity: The presence of a complete electrical circuit, necessary for consistent solenoid operation.
  
• Retract Position: The energized state where the solenoid pulls the rod inward, allowing fuel flow.
  

Symptoms of Failure and Field Observations
Operators have reported erratic behavior from the shutoff solenoid on the 850K Series 2. Common symptoms include:

• Engine starts and runs briefly, then shuts off unexpectedly
  
• Engine fires and dies immediately after ignition
  
• Solenoid fails to retract fully, requiring manual intervention
  
• Machine runs only when solenoid is physically tied back with wire
  

These issues often point to one of three root causes:

• Electrical continuity problems: Loose connectors, corroded terminals, or intermittent voltage supply
  
• Mechanical misalignment: Improper solenoid rod adjustment preventing full retraction
  
• Internal solenoid failure: Burned coils or worn plunger mechanisms
  

One technician described manually pushing the solenoid into the retracted position and feeling a “notch” where it seemed to hold temporarily. This tactile feedback suggests partial engagement, but without full retraction, the solenoid cannot maintain fuel flow under vibration and load.
Adjustment Procedure and Best Practices
Solenoids—even brand new ones—often require adjustment before installation. The correct procedure involves:

• Removing the solenoid from the pump
  
• Marking the stop lever’s position on the pump housing for reference
  
• Energizing the solenoid to confirm full retraction
  
• Manually pushing the solenoid rod to its maximum retracted position
  
• Aligning the rod with the stop lever’s marked position
  
• Adjusting the rod length or mounting bracket to ensure full engagement
  

Failure to retract fully can cause the solenoid to overheat and burn out, especially if it struggles to hold position against spring tension. Technicians recommend verifying voltage at the solenoid connector—typically 12V or 24V depending on system spec—and checking for clean, tight connections.
Electrical Diagnostics and Continuity Checks
To diagnose electrical issues:

• Use a multimeter to check voltage at the solenoid during key-on and engine-run states
  
• Inspect wiring harness for abrasion, pinching, or rodent damage
  
• Test continuity between solenoid terminals and battery ground
  
• Verify that relays and fuses in the shutdown circuit are functioning properly
  

In one case, a machine exhibited intermittent shutdowns traced to a corroded relay socket. Replacing the relay and cleaning the contacts resolved the issue. Another operator found that the solenoid boot had never been removed, suggesting the component had never been serviced—yet the machine required manual bumping of the solenoid to shut down, indicating wear or misalignment.
Anecdotes and Lessons from the Field
A contractor in Texas recalled tying back the solenoid with baling wire just to keep the machine running through a half-day of trenching. While effective short-term, this workaround risks fuel flooding and uncontrolled engine operation. Another mechanic shared a story of replacing the solenoid three times before discovering a voltage drop caused by a failing ignition switch.
These stories underscore the importance of holistic diagnostics—checking not just the solenoid, but the entire control circuit, mechanical linkage, and power supply.
Recommendations for Long-Term Reliability
To ensure consistent solenoid performance on the Case 850K Series 2:

• Perform regular inspections of solenoid mounting and rod alignment
  
• Clean and protect electrical connectors with dielectric grease
  
• Replace worn boots and seals to prevent moisture ingress
  
• Use OEM or high-quality aftermarket solenoids rated for continuous duty
  
• Document voltage readings and rod positions during service for future reference
  
• Train operators to recognize early signs of solenoid failure
  

Conclusion
The shutoff solenoid on the Case 850K Series 2 may be a small component, but its role is critical. When it fails, the machine becomes unpredictable, risking downtime and safety hazards. Through proper adjustment, electrical testing, and preventive maintenance, technicians can restore reliable operation and extend the life of both the solenoid and the dozer itself. In the world of heavy equipment, even the smallest part can carry the weight of the whole job.