08-13-2025, 05:11 PM
Experiencing no voltage to the fuel shutoff solenoid or glow plugs on a Bobcat 773F can be a challenging issue, often stemming from electrical or control system malfunctions. This guide provides a comprehensive approach to diagnosing and resolving such problems, incorporating insights from experienced technicians and real-world examples.
Understanding the System Components
An operator faced a similar issue with a Bobcat 773F after a complete engine rebuild. Despite having power to all relays, the trigger wires for the relays were not receiving power. By using a jumper wire, the fuel shutoff solenoid could be cycled, indicating a control signal issue. Further investigation revealed that the green/yellow wire from the ignition switch had been removed and rerouted, likely to bypass a malfunctioning BOSS system.
Solutions Implemented
Addressing no voltage issues to the fuel shutoff solenoid and glow plugs on a Bobcat 773F requires a systematic approach to diagnose and resolve underlying electrical or control system problems. By following the diagnostic steps outlined above and implementing preventive measures, operators can restore reliable operation to their equipment.
For a visual guide on troubleshooting glow plug issues in Bobcat machines, consider watching the following video:
Understanding the System Components
- Fuel Shutoff Solenoid: This solenoid controls the fuel flow to the engine. When the ignition is turned off, the solenoid disengages, stopping fuel delivery and shutting down the engine.
- Glow Plugs: These are heating elements used to preheat the engine's combustion chamber, facilitating easier starts in cold conditions.
- BOSS Controller: The Bobcat Operator Safety System (BOSS) controller manages various safety and operational functions, including the activation of the fuel shutoff solenoid and glow plugs.
- Blown Fuses or Faulty Relays: A blown fuse or malfunctioning relay can interrupt the power supply to the solenoid and glow plugs.
- Wiring Issues: Damaged or disconnected wires, especially in the engine harness, can prevent voltage from reaching critical components.
- BOSS Controller Malfunction: A faulty BOSS controller may fail to send the necessary signals to activate the solenoid and glow plugs.
- Bypassed Safety Features: Improper modifications, such as bypassing safety switches or relays, can lead to operational issues and safety concerns.
- Inspect Fuses and Relays: Check the fuse panel for any blown fuses related to the fuel system and glow plugs. Swap out relays with known good ones to rule out relay failure.
- Examine Wiring Connections: Thoroughly inspect the engine harness for any signs of wear, corrosion, or disconnections. Pay close attention to the green/yellow wire from the ignition switch, as improper connections here can bypass safety systems and cause issues.
- Test Voltage at Components: Use a multimeter to check for voltage at the fuel shutoff solenoid and glow plugs when the ignition is turned on. Lack of voltage indicates an upstream issue.
- Verify BOSS Controller Operation: Ensure the BOSS controller is receiving power and functioning correctly. A malfunctioning controller may not send the necessary activation signals.
An operator faced a similar issue with a Bobcat 773F after a complete engine rebuild. Despite having power to all relays, the trigger wires for the relays were not receiving power. By using a jumper wire, the fuel shutoff solenoid could be cycled, indicating a control signal issue. Further investigation revealed that the green/yellow wire from the ignition switch had been removed and rerouted, likely to bypass a malfunctioning BOSS system.
Solutions Implemented
- Rewiring: The operator restored the original wiring configuration, ensuring all connections were secure and properly routed.
- Component Replacement: Faulty relays and fuses were replaced with OEM parts to restore proper function.
- BOSS Controller Reset: The BOSS controller was reset to clear any stored faults and reestablish normal operation.
- Regular Maintenance: Conduct routine inspections of electrical components, including fuses, relays, and wiring, to identify potential issues before they cause failures.
- Avoid Unauthorized Modifications: Refrain from bypassing safety systems or making unauthorized electrical modifications, as these can lead to operational problems and safety hazards.
- Use OEM Parts: Always use original equipment manufacturer (OEM) parts for replacements to ensure compatibility and reliability.
Addressing no voltage issues to the fuel shutoff solenoid and glow plugs on a Bobcat 773F requires a systematic approach to diagnose and resolve underlying electrical or control system problems. By following the diagnostic steps outlined above and implementing preventive measures, operators can restore reliable operation to their equipment.
For a visual guide on troubleshooting glow plug issues in Bobcat machines, consider watching the following video:
