Troubleshooting Bobcat 773: No Voltage to Fuel Shut-Off Solenoid or Glow Plugs

[MikePhua]

When your Bobcat 773 skid steer starts showing issues like no voltage to the fuel shut-off solenoid or glow plugs, it’s crucial to act quickly. These issues are common in older or heavily used models, but with the right troubleshooting steps, most problems can be resolved without extensive repairs. Below, we break down common causes of these electrical issues and how to troubleshoot them effectively.
Understanding the Problem: No Voltage to Key Components
If you're experiencing no voltage to the fuel shut-off solenoid or glow plugs in your Bobcat 773, it can result in the machine failing to start. These two components are vital for the operation of the engine. The fuel shut-off solenoid controls fuel flow into the engine, and the glow plugs assist in the cold start process by warming the fuel system. When either of these components malfunctions due to lack of voltage, the machine won’t start, leaving operators frustrated and unable to complete their tasks.
Several possible causes could be responsible for this issue. Common culprits include electrical faults, problems with the ignition system, and wiring issues.
Common Causes and Troubleshooting Tips
1. Ignition Switch Failure
One of the most common causes of no voltage to the solenoid or glow plugs is a malfunctioning ignition switch. Over time, the ignition switch can wear out or become corroded, which may result in an intermittent or complete loss of voltage to the fuel shut-off solenoid and glow plugs.
Solution:
Test the ignition switch to ensure it’s sending the correct voltage when the key is turned. Use a multimeter to check for voltage at the ignition switch's output terminals. If no voltage is detected, it may be necessary to replace the ignition switch.
2. Faulty Relay or Fuse
The electrical relay and fuse that control the fuel shut-off solenoid and glow plugs are often overlooked but are essential for powering these components. A blown fuse or a faulty relay can prevent voltage from reaching the solenoid and glow plugs.
Solution:
Inspect the fuse box and relays related to the glow plugs and fuel shut-off solenoid. Replace any blown fuses and test the relays for continuity. If the relay is faulty, replace it to restore proper electrical function.
3. Broken or Corroded Wiring Connections
Another potential issue is a broken or corroded wiring connection. Wiring issues, especially on machines exposed to dirt, moisture, and vibrations, can cause intermittent electrical failures. Corrosion in connectors or wires can result in poor electrical conductivity, leading to voltage loss.
Solution:
Examine the wiring for signs of wear, corrosion, or loose connections, particularly near the solenoid, glow plugs, and ignition system. Clean or replace any corroded terminals and ensure all connections are secure. Pay attention to ground connections as well, as poor grounding can result in voltage issues.
4. Faulty Fuel Shut-Off Solenoid or Glow Plugs
While less common, a faulty fuel shut-off solenoid or glow plugs can cause the issue. If either of these components fails, it can result in no voltage being supplied to them, even if the rest of the electrical system is functioning.
Solution:
Test the solenoid and glow plugs by applying direct voltage from the battery to check if they activate. If they fail to function correctly, it may be necessary to replace them. However, before replacing parts, always ensure the wiring and connectors are intact.
5. Starter Relay or Battery Issues
If the voltage supply from the battery to the electrical components is insufficient, the fuel shut-off solenoid and glow plugs may not receive the power they need. This issue is often related to a weak or malfunctioning starter relay or a battery that’s nearing the end of its life.
Solution:
Test the battery voltage to ensure it's within the acceptable range (usually 12.6 to 12.8 volts for a healthy battery). Check the starter relay for proper operation, and ensure the battery terminals are clean and tightly connected.
Tips for Preventing Future Issues
Preventive maintenance is key to avoiding these issues down the road. Here are some tips to keep your Bobcat 773 running smoothly:

1. Regularly Inspect Electrical Components:
   Keep a close eye on the ignition switch, relays, fuses, and wiring. Clean the battery terminals and check connections to prevent corrosion.
   
2. Test Glow Plugs and Solenoids Periodically:
   Over time, glow plugs and fuel shut-off solenoids can degrade. Regularly test these components to identify early signs of failure and replace them as needed.
   
3. Use Quality Parts:
   When replacing parts such as the ignition switch or relays, always opt for high-quality, OEM parts to ensure proper function and longevity.
   
4. Check for Wiring Damage After Harsh Conditions:
   If your Bobcat 773 has been used in harsh conditions—such as wet or muddy environments—inspect the wiring and electrical components for any signs of wear, water ingress, or short circuits.
   
5. Keep the Battery in Good Condition:
   Batteries tend to lose efficiency over time. Make sure the battery is charged properly and replace it when necessary to avoid electrical issues.
   

Conclusion: Getting Your Bobcat 773 Back in Action
Electrical issues, such as no voltage to the fuel shut-off solenoid or glow plugs, can be a frustrating challenge. However, with the proper troubleshooting steps, you can identify the root cause and restore your Bobcat 773 to full functionality. Start by checking the ignition switch, relays, fuses, wiring, and the components themselves. Regular maintenance and timely replacements will help avoid these issues in the future, ensuring your equipment stays in top shape for years to come.
By understanding the most common causes of electrical failures and taking the time to diagnose and repair them, you can minimize downtime and get back to work without unnecessary delays. Happy digging!