Troubleshooting and Adjusting the Governor and Throttle on a Clark 666B Loader

[MikePhua]

The Clark 666B loader, an iconic piece of heavy machinery, is designed to handle a variety of tasks on construction sites, from material handling to earthmoving. However, like all machines, it can face mechanical issues, particularly in its idle and throttle control systems. A common issue many operators experience with the Clark 666B is that it won’t idle properly or maintain a steady idle speed. This often points to a problem with the governor or throttle setup.
This article will explore the potential causes of a rough or non-functioning idle on the Clark 666B, explain how the governor and throttle system work, and offer a step-by-step guide on how to diagnose and fix the problem. Additionally, we will provide tips on how to properly adjust the governor and throttle to ensure smooth idle performance.
Understanding the Governor and Throttle System
The governor and throttle system on the Clark 666B is designed to regulate engine speed and ensure that the engine runs efficiently at both idle and full throttle. The governor, in particular, is responsible for maintaining a steady idle speed by adjusting the throttle based on engine load and speed.

• Governor: The governor controls the engine speed by adjusting the fuel flow to the engine. It compensates for changes in load, ensuring that the engine maintains a consistent RPM (revolutions per minute) under varying conditions.
  
• Throttle: The throttle controls the amount of fuel and air mixture entering the engine. When you press the accelerator, the throttle opens, allowing more fuel and air into the engine, which increases the engine speed. When you release the pedal, the throttle closes, reducing the fuel and air flow, and the engine slows down.
  

A malfunction in either of these components can cause idle problems, such as the engine stalling, idling too high, or failing to maintain a steady idle speed.
Common Causes of Idle Problems in the Clark 666B
There are several common causes of idle problems in the Clark 666B loader, particularly related to the governor and throttle system. Here are some of the most frequent issues:

1. Dirty or Faulty Governor Mechanism:
   The governor system, which includes springs, linkages, and valves, can become clogged with dirt, grime, or old lubricants over time. This can cause the governor to become sluggish or unresponsive, preventing it from adjusting the throttle properly at idle.
   
2. Incorrect Governor Settings:
   The governor on the Clark 666B may become misadjusted, either due to wear and tear or improper handling during previous maintenance. This misadjustment can result in the engine idling too high or too low, or even stalling completely.
   
3. Throttle Linkage Issues:
   The throttle linkage can become loose, worn, or misaligned, causing the throttle to either stick in one position or fail to respond correctly to the accelerator pedal. If the linkage is too tight or too loose, it can affect the engine's idle speed.
   
4. Fuel System Problems:
   Fuel delivery problems, such as clogged fuel filters or dirty fuel injectors, can also affect idle performance. If the engine isn't receiving a consistent supply of fuel, it will struggle to maintain a steady idle speed.
   
5. Air Intake Blockages:
   Restricted airflow caused by a dirty air filter or intake manifold can reduce the engine's ability to maintain the proper idle speed. A blocked air filter can prevent enough air from entering the engine, which can lead to rough idling or stalling.
   
6. Vacuum Leaks:
   Leaks in the intake manifold, vacuum hoses, or throttle body can cause erratic idling. When there is a vacuum leak, the engine may receive more air than the throttle is prepared to regulate, causing it to run too lean (too much air) and potentially stall.
   

Diagnosing Idle Problems on the Clark 666B
To accurately diagnose idle issues on the Clark 666B loader, follow these steps:

1. Check the Governor Mechanism:
   • Inspect the governor for dirt or debris. Clean the governor parts carefully, especially the linkage and spring. If the governor is stuck or sluggish, it may need to be replaced or rebuilt.
     
   • Check for any wear or damage to the governor components. If the governor components appear worn out, they may need to be adjusted or replaced.
     
2. Inspect the Throttle Linkage:
   • Check the throttle linkage for signs of wear, binding, or misalignment. If the linkage is loose, tighten the connections to ensure smooth operation. If it’s too tight, loosen it slightly to allow for more movement.
     
   • Make sure that the linkage is not obstructed or sticking at any point in its range of motion.
     
3. Verify Fuel and Air Systems:
   • Check the fuel filter for clogs or contamination. A dirty or clogged fuel filter can restrict fuel flow, causing poor idle performance.
     
   • Inspect the fuel injectors for any signs of clogging or wear. Dirty injectors can cause uneven fuel delivery, affecting idle smoothness.
     
   • Inspect the air filter and intake system. Replace any clogged air filters, and check the intake manifold for leaks.
     
4. Check for Vacuum Leaks:
   • Inspect all vacuum hoses and gaskets for cracks or signs of leakage. If a leak is found, replace the damaged hoses or gaskets to restore proper vacuum pressure.
     
5. Test the Governor Settings:
   • Adjust the governor according to the manufacturer’s specifications. Typically, the governor should be adjusted so that it maintains the engine speed at the desired idle RPM. If the idle is too high or too low, adjust the governor settings using the correct tools.
     

How to Adjust the Governor and Throttle
Proper adjustment of the governor and throttle is essential to ensuring that the engine runs smoothly and maintains a stable idle speed. Here’s how you can adjust both systems:

1. Adjusting the Governor:
   • First, ensure that the engine is turned off and cool to the touch. This will prevent injury and ensure accurate adjustments.
     
   • Locate the governor control lever and the adjustment screw. These are usually found near the throttle linkages.
     
   • Adjust the screw or lever to set the engine speed to the desired idle RPM. Typically, the idle speed for the Clark 666B is around 800 to 1,000 RPM, but check the owner’s manual for the specific idle speed.
     
   • After adjusting, test the idle by starting the engine. If the idle is still rough or too high, fine-tune the governor adjustment until you achieve a smooth idle.
     
2. Adjusting the Throttle Linkage:
   • Check the throttle linkage for any play or slack. If the linkage is too loose, tighten the connections. If it is too tight, loosen the connections slightly to allow for smoother operation.
     
   • Ensure that the throttle pedal moves freely without binding. If the pedal feels stiff, lubricate the throttle linkage and check for any parts that may need to be replaced.
     

Real-World Case Study: Restoring Idle Performance
A construction company operating a Clark 666B loader experienced issues with the machine’s idle performance. The loader was struggling to maintain a steady idle and would often stall when the operator released the throttle. After performing a series of checks, the company’s mechanic discovered that the governor spring was clogged with dirt and debris, causing it to operate sluggishly. The mechanic cleaned the governor components, adjusted the idle RPM, and replaced the worn throttle linkage. After the adjustments, the loader’s idle returned to normal, and the engine ran smoothly.
Conclusion
A rough or non-functioning idle on the Clark 666B loader is often caused by issues with the governor, throttle linkage, or fuel and air systems. Diagnosing the problem requires a careful inspection of these components, and adjusting the governor and throttle system can usually restore normal engine performance. Regular maintenance of the governor and throttle systems, including cleaning, lubrication, and timely adjustments, can prevent idle issues from recurring. By following the steps outlined in this article, operators can ensure that their Clark 666B loader runs smoothly and reliably on the job.