Troubleshooting a Bobcat 751 That Won't Start: A Comprehensive Guide

[MikePhua]

The Bobcat 751, a compact skid steer loader, is a popular machine used in various industries like construction, landscaping, and agriculture. When it suddenly refuses to start, it can be a significant inconvenience, especially on the job site where time is money. Understanding the root causes of starting issues and following a structured troubleshooting process can help get the Bobcat 751 back up and running efficiently.
Common Causes for Starting Issues
Before diving into troubleshooting, it's important to recognize some common causes that may prevent the Bobcat 751 from starting:

• Dead or Weak Battery: A dead or weak battery is one of the most common culprits. The battery may be drained due to prolonged inactivity or simply because it's nearing the end of its lifespan.
  
• Starter Motor Problems: A malfunctioning starter motor can prevent the engine from turning over.
  
• Fuel Supply Issues: If the fuel system is compromised, the engine won't receive the necessary fuel to start.
  
• Electrical Problems: Loose or corroded wiring connections, faulty fuses, or damaged relays can all cause the Bobcat to fail to start.
  
• Faulty Ignition Switch: The ignition switch might fail, preventing the machine from turning on even though all other systems are operational.
  

Step-by-Step Troubleshooting Process
To troubleshoot a Bobcat 751 that won't start, follow this detailed process:
1. Check the Battery
The first thing you should do is inspect the battery. A low or dead battery can prevent the Bobcat 751 from starting.

• Test the Battery Voltage: Use a multimeter to check the battery’s voltage. A healthy, fully charged battery should read around 12.6 volts. If it’s lower than that, the battery may need charging or replacement.
  
• Inspect Battery Terminals: Check for any corrosion or loose connections at the battery terminals. Clean the terminals and tighten the connections if necessary.
  
• Jump Start the Bobcat: If the battery voltage is low, try jump-starting the machine with another vehicle or a jump starter. If the machine starts, you may need to replace the battery or check the charging system.
  

2. Examine the Starter Motor and Solenoid
If the battery is in good condition but the Bobcat still won't start, the starter motor could be the issue. The starter motor is responsible for turning the engine over when you start the machine.

• Listen for Clicking Sounds: When you turn the ignition key, listen for a clicking sound. If you hear a single click or multiple clicks, it could indicate a faulty starter motor or solenoid.
  
• Test the Starter: To test the starter motor, you may need to use a voltmeter to check if there is power reaching the starter when the ignition is turned on. If there's no power or insufficient power, the starter motor or solenoid could be faulty and may need replacing.
  

3. Inspect the Fuel System
If the engine turns over but doesn't start, the issue may lie with the fuel system. The Bobcat 751 relies on fuel to start, so any problems in the fuel supply can prevent it from starting.

• Check the Fuel Level: Ensure that the fuel tank is filled and the fuel is fresh. Stale or old fuel can cause starting issues.
  
• Inspect Fuel Lines: Look for any cracks, blockages, or leaks in the fuel lines. If fuel isn’t reaching the engine properly, the machine won’t start.
  
• Fuel Filter Inspection: A clogged fuel filter can prevent fuel from reaching the engine. Replace the fuel filter if it appears dirty or clogged.
  
• Check Fuel Pump: If the fuel filter and lines seem fine, inspect the fuel pump. A malfunctioning fuel pump can restrict the flow of fuel to the engine, resulting in starting problems.
  

4. Assess the Electrical System
The Bobcat 751 relies heavily on its electrical system for various functions, including starting the engine. If there's an electrical issue, it can prevent the machine from starting, even if everything else is in working order.

• Check Fuses and Relays: Inspect the fuses and relays in the Bobcat 751’s electrical system. A blown fuse or malfunctioning relay can prevent the machine from starting. Replace any damaged fuses or relays.
  
• Inspect Wiring Connections: Look for loose or corroded wiring connections, especially around the starter motor, ignition switch, and battery. Tighten or clean connections as needed.
  
• Test the Ignition Switch: A faulty ignition switch could prevent power from reaching critical components. Test the ignition switch by checking if power is sent to the starter and other necessary systems when the key is turned.
  

5. Test the Safety Switches
Bobcat machines are equipped with safety switches designed to prevent the engine from starting in unsafe conditions.

• Seat Switch: Ensure that the seat switch is functioning properly. If it detects that the operator is not seated, it may prevent the engine from starting.
  
• Hydraulic Safety Switch: Check the hydraulic safety switch, as it prevents starting when the hydraulic system is under pressure.
  
• Park Brake Switch: Verify that the park brake is fully engaged, as the machine may not start if the park brake is not activated.
  

6. Inspect the Glow Plugs (If Diesel)
If you have a diesel engine in your Bobcat 751, glow plugs are essential for cold starts. Faulty glow plugs can prevent the engine from firing.

• Test the Glow Plugs: Use a multimeter to check the resistance of the glow plugs. If any glow plugs are faulty, they will need to be replaced.
  

7. Check the Engine Control Module (ECM)
In some cases, a malfunctioning Engine Control Module (ECM) may prevent the Bobcat 751 from starting. The ECM is the brain of the machine, controlling various functions, including the starting process.

• Diagnostic Codes: If you have access to a diagnostic tool, check for any error codes from the ECM. These codes can pinpoint issues that may be preventing the machine from starting.
  
• Resetting the ECM: Sometimes, simply resetting the ECM can resolve issues. Disconnect the battery for a few minutes to reset the ECM and see if that solves the problem.
  

Conclusion: Get Your Bobcat 751 Running Again
When your Bobcat 751 won’t start, it’s essential to approach troubleshooting methodically. By systematically checking the battery, starter motor, fuel system, electrical connections, safety switches, and other components, you can diagnose and fix the problem efficiently. If the issue persists after following these steps, it may be time to consult a professional mechanic or Bobcat technician.
Whether you're working in construction, landscaping, or any other industry that relies on skid steers, understanding the key issues that cause starting problems and knowing how to troubleshoot them can save you valuable time and money.