Troubleshooting Engine Stalling Issues on Hitachi EX120-2 Excavator

[MikePhua]

The Hitachi EX120-2 is a well-regarded mid-size hydraulic excavator known for its reliability and durability on construction sites. However, like any piece of heavy machinery, it is not immune to issues. One common problem that can arise with the EX120-2 is the engine stalling or shutting down unexpectedly. This can lead to costly downtime and disrupt operations, so understanding the potential causes and solutions is critical for machine owners and operators.
Common Causes of Engine Stalling
Engine stalling can be caused by a variety of issues, ranging from fuel system problems to electrical malfunctions. Here are some of the most common causes of engine stalling on the Hitachi EX120-2 and other similar machines:

1. Fuel System Problems
   • Fuel delivery issues are one of the primary causes of engine stalling. The EX120-2 relies on a well-functioning fuel system to provide a steady supply of clean fuel to the engine. If there is a blockage, air in the fuel lines, or a failing fuel pump, the engine may starve for fuel and stall.
     
   • Solution: Inspect the fuel filter and fuel lines for clogs or leaks. Replace the fuel filter if it’s dirty or clogged. Ensure that the fuel tank is clean and that the fuel pump is working properly. Check for air in the fuel lines and bleed the system if necessary.
     
2. Air Filter Blockage
   • A clogged air filter can reduce the amount of air entering the engine, causing it to run inefficiently or stall. The engine requires a certain air-fuel ratio to operate smoothly, and a blocked air filter disrupts this balance.
     
   • Solution: Regularly inspect the air filter for dirt and debris. Clean or replace the air filter as needed to ensure proper airflow to the engine.
     
3. Electrical Issues
   • The EX120-2’s engine is controlled by an electronic system that includes sensors and wiring for fuel delivery, engine speed, and other critical functions. A fault in the electrical system, such as a bad sensor, loose wiring, or a failing alternator, can cause the engine to stall.
     
   • Solution: Check all electrical connections for corrosion or loose wires. Inspect the alternator for proper operation and check the battery voltage. If any sensors are malfunctioning, they may need to be replaced.
     
4. Fuel Contamination
   • Contaminated fuel is a common problem that can cause engine stalling. Water or dirt in the fuel can clog the injectors, causing poor fuel combustion and ultimately stalling the engine.
     
   • Solution: Drain the fuel tank and replace the contaminated fuel with clean fuel. Consider using a fuel additive to help clean the fuel system and prevent future contamination.
     
5. Overheating
   • If the engine temperature gets too high, it can cause the engine to stall. Overheating may be due to a coolant leak, a faulty radiator, or a blocked cooling system.
     
   • Solution: Check the coolant level and condition. Inspect the radiator and cooling fan for proper operation. Ensure that there are no leaks in the cooling system and that the engine is not overheating.
     
6. Throttle or Governor Issues
   • The throttle controls the amount of air and fuel entering the engine, while the governor maintains the engine speed. A malfunctioning throttle or governor can cause the engine to lose power and stall.
     
   • Solution: Inspect the throttle linkage for wear or damage. Check the governor settings to ensure that it is properly regulating the engine speed. If necessary, recalibrate the governor or replace any faulty parts.
     
7. Injector Problems
   • The fuel injectors play a crucial role in delivering fuel to the engine. If the injectors are clogged or malfunctioning, the engine may stall due to improper fuel delivery.
     
   • Solution: Check the fuel injectors for clogs or leaks. Clean or replace the injectors if necessary to restore proper fuel delivery.
     
8. Excessive Engine Load
   • If the engine is overloaded, it can lead to stalling. This is often caused by operating the machine beyond its capacity or using the wrong attachments.
     
   • Solution: Ensure that the machine is operating within its recommended load limits. Avoid using attachments that may cause excessive strain on the engine, and monitor the load closely during operation.
     

Diagnosing and Fixing the Problem
When dealing with engine stalling, it’s essential to approach the problem methodically. Start by inspecting the fuel system, as this is the most common culprit. Check for leaks, clogs, or damage to the fuel filter, lines, and tank. If the fuel system appears to be functioning correctly, move on to the air filter and electrical system.
If the engine stalls only under certain conditions, such as heavy load or high temperatures, overheating or excessive load may be the issue. Check the cooling system and ensure that the machine is not being overworked. Use diagnostic tools if necessary to check for faults in the electrical system, such as malfunctioning sensors or wiring.
Preventative Maintenance to Avoid Stalling
Preventing engine stalling is far better than dealing with it once it occurs. Regular maintenance is the key to keeping your Hitachi EX120-2 running smoothly. Here are some preventative measures you can take:

• Fuel System Maintenance: Regularly check and replace the fuel filter to ensure clean fuel delivery. Keep the fuel tank and fuel lines free from debris, and use fuel additives to prevent contamination.
  
• Air Filter Inspection: Clean or replace the air filter every few months or after every major use. A clean air filter is crucial for maintaining engine performance.
  
• Electrical System Checks: Inspect electrical connections regularly and ensure that the battery is charged. Use a multimeter to check the voltage and diagnose any electrical issues.
  
• Cooling System Monitoring: Keep the coolant level at the proper level and ensure the radiator is free from dirt or debris. Overheating is a major cause of engine stalling and can be prevented with regular checks of the cooling system.
  
• Load Management: Avoid operating the machine at full capacity for extended periods. Be mindful of the machine’s load limits and ensure that the attachments are compatible with the excavator’s capabilities.
  

Conclusion
Engine stalling on the Hitachi EX120-2 can be a frustrating issue, but with proper diagnostics and regular maintenance, it can be prevented or quickly resolved. Whether the problem lies within the fuel system, the electrical components, or the engine itself, understanding the causes of stalling and taking proactive steps to address them will keep your machine running smoothly. By following a preventive maintenance schedule, you can extend the life of your excavator and minimize downtime, ensuring maximum productivity on the job site.