Bobcat T320 Shuts Down After Starting Due to Fuel Solenoid or Safety Interlock Failures

[MikePhua]

The Bobcat T320 and Its Control System
The Bobcat T320 compact track loader was introduced in the mid-2000s as one of the most powerful machines in Bobcat’s lineup at the time. With a rated operating capacity of 3,200 pounds and a turbocharged 81-horsepower diesel engine, it was designed for heavy-duty grading, land clearing, and material handling. Bobcat, founded in 1947, built its reputation on compact equipment, and the T320 was a flagship model in the CTL (compact track loader) segment until it was replaced by the T870.
The T320 features an electronically controlled engine shutdown system, which includes a fuel shutoff solenoid, seat bar sensor, and interlock control module. These components work together to ensure the machine only runs when all safety conditions are met.
Symptoms of Immediate Shutdown
A common issue reported by operators is that the T320 starts normally but shuts down within 2–5 seconds, often without displaying any diagnostic codes. This behavior typically points to one of the following:

• Fuel solenoid not staying energized
  
• Seat bar or seat switch not registering operator presence
  
• Interlock control module failing to maintain run signal
  
• Wiring harness damage or corrosion at connectors
  

In one case, a machine would start and immediately die unless the operator manually held the fuel solenoid open. This confirmed that the solenoid was not receiving a sustained signal from the control system.
Fuel Solenoid and Relay Diagnostics
The fuel shutoff solenoid is a critical component that controls fuel flow to the injection pump. It is energized by a relay controlled by the interlock module. If the solenoid loses power, the engine will shut down as a safety measure.
To test the solenoid:

• Turn the key to the run position and listen for a click at the solenoid
  
• Start the engine and observe whether the solenoid retracts and stays engaged
  
• If it retracts briefly and then releases, check the relay and wiring
  
• Bypass the relay temporarily to confirm solenoid function
  

If the solenoid works when powered directly, the issue lies upstream—likely with the relay, interlock module, or safety switches.
Safety Interlock and Seat Bar Switches
The T320 uses a seat bar sensor and seat switch to detect operator presence. If either fails or becomes misaligned, the interlock module will shut down the engine. These switches are prone to wear, especially in machines used in dusty or wet environments.
To troubleshoot:

• Inspect the seat bar switch for continuity when lowered
  
• Check the seat switch under the cushion for proper operation
  
• Clean connectors and apply dielectric grease to prevent corrosion
  
• Use a multimeter to verify voltage at the interlock module during startup
  

Additional Considerations

• Check for blown fuses or loose grounds near the control module
  
• Inspect the wiring harness near the engine bay for rodent damage or abrasion
  
• Ensure the battery voltage is stable—low voltage can cause erratic module behavior
  
• If equipped with a keyless panel, verify that the security system is not locking out the start sequence
  

Conclusion
A Bobcat T320 that shuts down seconds after starting is often experiencing a failure in the fuel solenoid circuit or safety interlock system. By methodically testing the solenoid, relays, and operator presence switches, technicians can isolate the fault and restore reliable operation. These machines are built with safety in mind, and even a minor sensor fault can trigger a shutdown. With careful diagnostics and attention to wiring integrity, the issue can be resolved without unnecessary parts replacement.