Troubleshooting Unintended Throttle Surge in the Ford 655A Backhoe

[MikePhua]

Introduction
Experiencing an unexpected increase in engine speed, commonly referred to as "throttling up on its own," in a Ford 655A backhoe can be both perplexing and concerning. This issue often stems from the fuel system, particularly the fuel injection pump and its associated components. Understanding the underlying causes and implementing appropriate solutions can restore normal operation and prevent further complications.
Understanding the Fuel Injection Pump and Governor Mechanism
The Ford 655A backhoe is equipped with a Simms or similar mechanical fuel injection pump, which regulates the amount of fuel delivered to the engine based on throttle input. This system includes a governor that maintains engine speed by adjusting the fuel delivery in response to load changes. If the governor or related components malfunction, it can lead to unintended throttle surges.
Common Causes of Unintended Throttle Surge

1. Sticking Governor Components: Over time, the governor's flyweights and control rack can become sticky due to varnish buildup or lack of lubrication. This can cause the governor to stick in a higher fuel delivery position, resulting in increased engine speed.
   
2. Contaminated Fuel: Dirty or contaminated fuel can cause debris to enter the fuel injection pump, leading to erratic fuel delivery and engine surging.
   
3. Improper Fuel Pump Lubrication: The fuel injection pump requires proper lubrication to function correctly. Insufficient oil levels can cause internal components to seize or operate erratically.
   
4. Faulty Governor Springs: The governor relies on springs to regulate fuel delivery. Worn or broken springs can lead to improper fuel regulation and surging.
   

Diagnostic Steps

1. Inspect Fuel Quality: Check the fuel for signs of contamination or water. Replace the fuel filter if necessary and ensure the fuel lines are clear.
   
2. Examine Fuel Injection Pump Oil Levels: Locate the oil fill plug on the side of the fuel injection pump. Using a 1/2-inch wrench, remove the plug and check the oil level. If the oil is low, add clean engine oil until it reaches the full mark. If the oil appears dirty or contaminated, drain and replace it.
   
3. Check Governor Operation: With the engine off, manually move the governor control rack through its full range. It should move smoothly without binding. If resistance is felt, the governor may need cleaning or internal inspection.
   
4. Inspect Governor Springs: Remove the governor cover and inspect the springs for wear or damage. Replace any defective springs.
   

Preventive Measures

• Regular Maintenance: Perform routine maintenance on the fuel system, including replacing fuel filters and checking for leaks.
  
• Use Clean Fuel: Always use clean, filtered fuel to prevent contamination of the fuel system.
  
• Proper Lubrication: Ensure the fuel injection pump is properly lubricated to prevent internal wear and sticking components.
  
• Monitor Engine Performance: Regularly monitor engine performance for signs of irregularities, such as surging or unusual noises.
  

Conclusion
Unintended throttle surging in the Ford 655A backhoe is often a result of issues within the fuel injection system, particularly the governor mechanism. By systematically diagnosing and addressing potential causes, such as contaminated fuel, improper lubrication, or faulty governor components, operators can restore normal engine function and prevent future occurrences. Regular maintenance and vigilance are key to ensuring the longevity and reliability of the backhoe's engine.