Troubleshooting and Maintaining the Cummins 855 Engine

[MikePhua]

The Cummins 855 is a robust, inline-six diesel engine renowned for its durability and performance. Widely used in construction machinery, trucks, and agricultural equipment, this engine has a reputation for being reliable under heavy loads. However, like all engines, it requires proper maintenance and troubleshooting when issues arise. In this article, we will explore common issues with the Cummins 855 engine, their causes, and how to diagnose and address them.
Overview of the Cummins 855 Engine
The Cummins 855 is part of Cummins' B-Series engine lineup, offering a variety of configurations for different power outputs. It is known for its simple, mechanical fuel system, making it easy to work on compared to modern electronic engines. Despite its age, the 855 remains popular due to its reliability and ease of maintenance.
Key Features of the Cummins 855:

• Configuration: Inline-six, 14.0L displacement
  
• Fuel System: Mechanical injection system (some models may have a Bosch or CAV pump)
  
• Applications: Heavy-duty trucks, industrial equipment, construction machinery, marine applications
  
• Power Output: Typically ranges from 250 to 400 horsepower, depending on the variant
  

Common Issues with the Cummins 855
Though the Cummins 855 is known for its longevity, it is not immune to certain problems. Here are some of the most common issues that owners or operators of the Cummins 855 engine might encounter.
1. Poor Starting or Hard Starting
One of the most common complaints with the Cummins 855 engine is difficulty starting, especially in cold weather. The engine’s mechanical fuel system can sometimes be tricky to start if certain components aren’t in optimal condition.

• Possible Causes:
  • Weak or Faulty Batteries: Inadequate cranking power can prevent the engine from starting properly.
    
  • Fuel System Issues: Clogged filters or air in the fuel lines can prevent fuel from reaching the injectors.
    
  • Glow Plugs: If the glow plugs are not working correctly, starting in cold temperatures becomes more difficult.
    
• Diagnostic Steps:
  • Check Battery Voltage: Ensure the battery is fully charged and capable of providing sufficient power.
    
  • Inspect Fuel Filters: Replace any clogged fuel filters and inspect the lines for leaks or air pockets.
    
  • Test Glow Plugs: Replace malfunctioning glow plugs to ensure proper preheating during cold starts.
    

2. Loss of Power or Poor Acceleration
Another common issue is a noticeable loss of power or sluggish acceleration, especially when the engine is under load. This can be caused by a variety of factors.

• Possible Causes:
  • Fuel Delivery Problems: Clogged injectors, a malfunctioning fuel pump, or low fuel pressure can all affect the engine’s power output.
    
  • Turbocharger Issues: If the turbocharger is not functioning correctly, the engine may lack the boost it needs for proper acceleration.
    
  • Air Intake or Exhaust Restrictions: Dirty air filters or a blocked exhaust can choke the engine and reduce power.
    
• Diagnostic Steps:
  • Check Fuel System: Inspect the fuel lines, pump, and injectors for wear or damage. Replace clogged or malfunctioning components.
    
  • Examine the Turbocharger: Ensure the turbo is spinning freely and the seals are intact.
    
  • Inspect Filters: Replace the air and fuel filters to improve airflow and fuel delivery.
    

3. Excessive Smoke or Black Smoke
Excessive smoke coming from the exhaust is a concern for many diesel engine owners. Black smoke, in particular, can indicate poor combustion, which is often caused by fuel system problems.

• Possible Causes:
  • Over-fueling: This can be caused by a malfunctioning fuel injection pump or improperly adjusted injectors.
    
  • Low Compression: Worn piston rings or valves can lead to low compression and poor combustion.
    
  • Air/Fuel Mixture: An improper balance between air and fuel can cause incomplete combustion, leading to smoke.
    
• Diagnostic Steps:
  • Inspect Fuel Injectors: Test the injectors for proper spray patterns and replace any that are faulty.
    
  • Check Compression: Perform a compression test to check for low compression in any cylinder.
    
  • Adjust Fuel Pump: Ensure the fuel pump is set to the correct fuel delivery rate and that it is functioning properly.
    

4. Overheating
Overheating can be a serious issue, leading to engine damage if not addressed. The Cummins 855 relies on a cooling system that includes a radiator, thermostat, and coolant lines.

• Possible Causes:
  • Low Coolant Levels: A common cause of overheating is simply low coolant levels due to leaks or evaporation.
    
  • Clogged Radiator: A radiator that is clogged with dirt or debris can significantly reduce the engine’s ability to cool properly.
    
  • Faulty Thermostat: A malfunctioning thermostat can prevent coolant from circulating properly, leading to overheating.
    
• Diagnostic Steps:
  • Check Coolant Level: Ensure the radiator is filled to the proper level and that there are no visible leaks.
    
  • Inspect Radiator: Clean the radiator fins and ensure that air can flow freely through the cooling system.
    
  • Test the Thermostat: Replace any faulty thermostats to ensure proper temperature regulation.
    

5. Oil Consumption or Leaks
Excessive oil consumption or visible oil leaks around the engine is another concern for Cummins 855 owners. This issue may be indicative of wear or seal failures in the engine.

• Possible Causes:
  • Worn Seals or Gaskets: Leaks can occur around seals and gaskets, especially those on the valve cover or oil pan.
    
  • Piston Ring Wear: Worn piston rings can cause excessive oil consumption due to poor sealing in the cylinders.
    
• Diagnostic Steps:
  • Inspect Gaskets and Seals: Check all gaskets and seals for any signs of wear or leaks, and replace any that are damaged.
    
  • Check Oil Consumption: Monitor oil levels over time to determine if oil consumption is excessive. If it is, a compression test can help identify worn piston rings.
    

General Maintenance Tips for the Cummins 855
To keep your Cummins 855 engine running smoothly, regular maintenance is essential. Below are some key maintenance tasks to help extend the life of the engine and prevent issues from arising:

• Change Oil Regularly: Follow the manufacturer’s recommendations for oil change intervals, typically every 250 to 500 hours of operation.
  
• Replace Fuel Filters: Change the fuel filters regularly to ensure the fuel system is free of contaminants.
  
• Check the Cooling System: Regularly inspect the radiator and cooling system for any blockages or leaks.
  
• Monitor Air Filters: Ensure that the air filters are clean and free of debris to promote optimal engine performance.
  
• Inspect Belts and Hoses: Regularly check belts and hoses for wear or cracking and replace as necessary.
  

Conclusion
The Cummins 855 is a powerful, durable engine commonly found in many industrial applications. While it’s known for its reliability, proper maintenance and timely troubleshooting are key to keeping it running smoothly. By understanding common issues such as starting problems, loss of power, excessive smoke, overheating, and oil leaks, you can address them quickly and ensure that your engine operates at peak efficiency for years to come. Regular maintenance and a proactive approach to troubleshooting are the best ways to extend the lifespan of this workhorse engine.