Old Cummins Compression Release Mounting: Common Issues and Solutions

[MikePhua]

The Cummins compression release mechanism is a critical part of the engine's start-up process, particularly in diesel engines where the compression ratio is much higher than in gasoline engines. These systems help reduce the strain on the engine during startup, allowing for easier cranking. However, over time, the compression release mounting system can experience issues, particularly in older models. This article will explore the role of the compression release system, common issues with the mounting, and how to fix or maintain it for optimal engine performance.
The Role of the Compression Release System
In diesel engines like those made by Cummins, the compression release system temporarily reduces the compression in one or more cylinders during engine cranking. This decreases the load on the starter motor and helps the engine start more easily, especially in colder temperatures or when the engine is under heavy load. Once the engine begins running, the system disengages, allowing full compression to return for normal operation.
The compression release system is typically controlled by an external linkage or solenoids, and it functions by holding open one or more valves in the cylinder head. This prevents the air-fuel mixture from being compressed during the starting phase, effectively reducing the torque needed to turn the engine over.
Compression Release Mounting Issues
Over time, the compression release mechanism on older Cummins engines can develop issues, especially if the mounting system is worn, improperly adjusted, or subjected to excessive stress. Here are some of the most common problems that can arise:

1. Worn or Damaged Mounting Brackets
   The mounting brackets for the compression release system hold the solenoids or linkage in place, ensuring that the system functions properly. Over time, these brackets can wear out or become damaged, leading to misalignment or failure of the compression release system. When this happens, the system might not engage or disengage properly, causing difficulty during startup or erratic engine performance.
   Solution:
   • Inspect the mounting brackets for signs of wear, cracks, or corrosion.
     
   • If the brackets are damaged, they should be replaced. Some operators have had success fabricating their own replacement brackets, but it’s essential to match the exact specifications of the original parts.
     
   • Ensure that all bolts and fasteners are tightly secured to avoid any play in the mounting.
     
2. Improper Adjustments or Misalignment
   Misalignment of the compression release mechanism can cause the system to operate inefficiently. If the linkage is not correctly adjusted, it may not fully open or close the valves, affecting the engine's ability to start smoothly. This can lead to increased wear on the starter motor, slow cranking, or even failure to start in some cases.
   Solution:
   • Check the linkage for proper adjustment. Many Cummins engines will have a service manual with specific instructions for setting the correct clearances.
     
   • If the system uses solenoids, check their alignment to ensure they are properly engaging and disengaging the valves.
     
   • If the engine struggles to start, an adjustment may be needed to ensure full valve release during cranking.
     
3. Wear on the Valve Lifters
   In some cases, the compression release system relies on valve lifters to hold the valves open temporarily. Over time, these lifters can become worn, which will affect their ability to open the valves properly. This can cause poor cranking, excessive wear on the starter motor, or difficulty starting the engine.
   Solution:
   • Inspect the valve lifters for any signs of wear or pitting. If necessary, replace the lifters to restore proper operation of the compression release system.
     
   • Ensure that the valve seats are in good condition as well. Worn valve seats can prevent proper sealing, leading to inefficient engine performance.
     
4. Faulty Solenoids or Electrical Components
   Many Cummins engines use electric solenoids to activate the compression release mechanism. These solenoids can fail due to electrical issues, such as a short circuit, poor wiring connections, or failure of the solenoid itself. When the solenoid fails, the compression release system may not function, leading to hard starting or even engine damage in extreme cases.
   Solution:
   • Check the wiring and connections leading to the solenoid for any signs of wear or damage.
     
   • Test the solenoid with a multimeter to ensure it is receiving proper voltage and is activating correctly.
     
   • If the solenoid is faulty, replace it with an OEM part to ensure compatibility and reliability.
     

Real-World Application: Troubleshooting a Cummins 6BTA Compression Release System
A mechanic working on a Cummins 6BTA engine, commonly found in industrial and marine applications, reported difficulty starting the engine, particularly in colder weather. After some troubleshooting, it was discovered that the compression release mounting brackets had become misaligned, preventing the valves from opening fully during startup.
By adjusting the linkage and ensuring that the solenoids were properly aligned, the mechanic was able to restore the compression release system’s functionality. The engine then cranked smoothly, and the issue was resolved without needing a full replacement of parts. This example highlights the importance of maintaining the mounting and linkage system, as even a small misalignment can have significant consequences.
Preventative Maintenance for the Compression Release System
Maintaining the compression release mounting and associated components is key to ensuring smooth operation and longevity of the engine. Here are a few maintenance tips:

1. Regular Inspection: Check the mounting brackets, solenoids, and linkages for signs of wear or misalignment. Catching issues early can prevent more serious problems down the line.
   
2. Lubrication: Ensure that all moving parts within the compression release system are properly lubricated to prevent excessive wear. Use the recommended lubricant specified in the owner’s manual.
   
3. Check Electrical Connections: Inspect the wiring to the solenoids for corrosion or damage, especially in areas where the wiring is exposed to moisture or heat. Proper electrical connections are critical for reliable solenoid function.
   
4. Keep the System Clean: Dirt and debris can accumulate in the compression release system, causing parts to stick or wear more quickly. Keep the system clean to ensure smooth operation.
   
5. Timely Replacements: If you notice any components such as the solenoids, mounting brackets, or valve lifters are starting to wear, replace them promptly to avoid bigger problems. Using OEM (Original Equipment Manufacturer) parts ensures proper fit and function.
   

Conclusion
The compression release system on older Cummins engines is an essential feature that helps make starting the engine easier, especially in tough conditions. However, like all systems, it is prone to wear and tear over time. Issues with the compression release mounting can lead to starting problems, erratic performance, and increased wear on the starter motor.
By regularly inspecting the mounting brackets, adjusting the linkage, checking the solenoids, and maintaining the valve lifters, operators can keep the system functioning optimally. A little preventative maintenance can go a long way in ensuring smooth engine starts and extending the life of the engine.
Whether you’re dealing with a simple misalignment or replacing faulty solenoids, understanding the mechanics behind the compression release system is key to keeping your Cummins engine running at its best. And just like many operators who have learned the hard way, knowing how to diagnose and fix these problems early can save both time and money in the long run.