Bobcat T320 Shutdown After Start and Diagnostic Pathways

[MikePhua]

The T320 and Bobcat’s Track Loader Evolution
The Bobcat T320 was introduced in the mid-2000s as part of Bobcat’s high-performance compact track loader lineup. With a rated operating capacity of 3,200 pounds and a turbocharged 89-horsepower diesel engine, the T320 was designed for demanding applications in grading, land clearing, and heavy material handling. Its rubber track system allowed for low ground pressure and excellent traction in mud, snow, and sand.
Bobcat, founded in 1947, became a global leader in compact equipment through its innovation in skid steers and track loaders. The T320 was one of the most powerful models in its class at the time, often used in tandem with hydraulic attachments like mulchers, trenchers, and augers. Despite its robust design, the T320’s reliance on electronic control modules and safety interlocks means that startup issues can be complex and frustrating.
Symptoms of Immediate Shutdown After Start
Operators encountering this issue typically report:

• Engine starts normally but shuts down within 3–10 seconds
  
• No fault codes displayed on the monitor
  
• Fuel level appears normal
  
• Glow plug and starter function as expected
  
• Machine does not respond to throttle input
  
• Safety bar and seat switch appear functional
  

These symptoms suggest that the shutdown is triggered by an electronic or sensor-based interlock rather than a mechanical fault. The absence of diagnostic codes complicates troubleshooting, as the system may not recognize the fault as critical or may fail to log it due to communication issues.
A contractor in Alberta experienced repeated shutdowns on his T320. After bypassing the seat switch and inspecting the fuel solenoid, he discovered a loose ground wire near the ECU. Re-securing the connection restored normal operation.
Electronic Control and Safety Interlocks
The T320 uses a combination of sensors and control modules to manage startup and operation. Key components include:

• Engine Control Module (ECM)
  
• Loader Control Module (LCM)
  
• Safety Interlock System (seat switch, lap bar, door sensor)
  
• Fuel shutoff solenoid
  
• CAN bus communication network
  

If any of these systems fail to confirm safe operating conditions, the ECM may shut down the engine to prevent damage or injury. Common failure points include:

• Faulty seat switch or intermittent lap bar sensor
  
• Corroded connectors at the fuel solenoid
  
• Weak battery voltage causing module reset
  
• Grounding issues at the frame or battery terminals
  
• CAN bus communication loss between ECM and LCM
  

A technician in Finland diagnosed a T320 with similar symptoms and found that the fuel solenoid was receiving voltage only during cranking. After replacing the relay and cleaning the fuse block, the machine stayed running.
Fuel Delivery and Solenoid Behavior
The fuel shutoff solenoid controls diesel flow to the injection pump. If it fails to remain energized after cranking, the engine will start and then die. Key inspection steps:

• Test voltage at solenoid during and after cranking
  
• Listen for audible click when key is turned
  
• Check for corrosion or loose terminals
  
• Inspect relay and fuse associated with solenoid circuit
  
• Verify continuity from ignition switch to solenoid
  

In one case, a crew in Texas found that the solenoid wire had rubbed against the frame and shorted. After replacing the wire and adding protective loom, the issue was resolved.
Sensor Overrides and Diagnostic Workarounds
To isolate the fault, operators may temporarily bypass certain sensors:

• Jumper seat switch terminals to simulate operator presence
  
• Disconnect lap bar sensor and test continuity
  
• Bypass door sensor if equipped
  
• Use external power source to energize fuel solenoid
  

These steps should only be used for diagnosis and not as permanent solutions. Safety systems are critical for operator protection and must be restored after testing.
A rental company in Oregon added a diagnostic toggle switch to simulate seat switch engagement during troubleshooting. This allowed technicians to confirm that the shutdown was not caused by operator presence logic.
Preventive Measures and Long-Term Reliability
To avoid future shutdown issues:

• Inspect and clean all electrical connectors quarterly
  
• Replace worn seat switches and lap bar sensors
  
• Use dielectric grease on solenoid terminals
  
• Test battery voltage and replace weak units
  
• Secure ground straps and verify continuity to frame
  
• Update software on control modules if available
  

A fleet manager in Alaska implemented a seasonal electrical inspection protocol for his T320 units. By checking voltage drop and connector integrity before winter, he reduced startup failures by 80%.
Stories from the Field
In Michigan, a T320 used for snow removal began shutting down after startup. The operator traced the issue to a cracked fuse block that allowed moisture intrusion. After replacing the block and sealing the compartment, the machine ran reliably through the season.
In Poland, a contractor retrofitted his T320 with a manual fuel shutoff valve after repeated solenoid failures. While not factory-approved, the modification allowed the machine to operate in remote areas without electronic shutdowns.
Conclusion
When a Bobcat T320 shuts down seconds after starting with no fault codes, the root cause often lies in the fuel solenoid circuit, safety interlocks, or electronic communication. With methodical diagnostics and attention to grounding and sensor integrity, operators can restore reliable performance. In a machine built for power and precision, staying running is the first step toward getting the job done.