08-04-2025, 07:55 PM
The John Deere 120 Excavator is a versatile and reliable piece of equipment used in various construction and excavation applications. However, like all machines, it can experience issues that affect its performance. One of the more frustrating problems that operators may face is when the excavator will not run effectively under load or while performing heavy tasks. This issue can manifest as a loss of power, stalling, or rough operation, making it difficult to complete essential work efficiently.
In this article, we will explore the common causes of this issue and provide a detailed guide to troubleshooting and resolving the problem. By understanding the underlying causes and following the correct steps, operators can diagnose and address the issue before it leads to more severe problems or prolonged downtime.
Common Symptoms and Causes of Loss of Power Under Load
The John Deere 120 Excavator is a durable and powerful machine, but it can face issues with running under load that can affect productivity. By understanding the common causes of power loss, such as fuel delivery problems, hydraulic issues, overheating, and electrical system malfunctions, operators can troubleshoot and resolve these problems effectively. Regular maintenance, including checking the fuel system, hydraulic components, cooling system, and electrical system, will ensure that the excavator performs reliably, even under demanding conditions.
By addressing these potential issues early and keeping up with preventive maintenance, operators can maximize the lifespan and performance of their equipment, reducing costly downtime and improving overall efficiency on the job site.
In this article, we will explore the common causes of this issue and provide a detailed guide to troubleshooting and resolving the problem. By understanding the underlying causes and following the correct steps, operators can diagnose and address the issue before it leads to more severe problems or prolonged downtime.
Common Symptoms and Causes of Loss of Power Under Load
- Loss of Engine Power
- Symptoms: One of the most noticeable symptoms of this problem is a significant loss of engine power when the machine is under load. The excavator may run smoothly during idle or light operation but struggle when digging or lifting heavy loads.
- Possible Causes:
- Fuel delivery issues: A clogged fuel filter, malfunctioning fuel pump, or contaminated fuel can limit the amount of fuel reaching the engine, resulting in insufficient power when the machine is under load.
- Air intake problems: A blocked air filter or issues with the air intake system can restrict airflow to the engine, causing poor combustion and decreased power under load.
- Exhaust blockages: If the exhaust system is partially clogged, it can cause back pressure, restricting engine performance.
- Fuel delivery issues: A clogged fuel filter, malfunctioning fuel pump, or contaminated fuel can limit the amount of fuel reaching the engine, resulting in insufficient power when the machine is under load.
- Symptoms: One of the most noticeable symptoms of this problem is a significant loss of engine power when the machine is under load. The excavator may run smoothly during idle or light operation but struggle when digging or lifting heavy loads.
- Hydraulic System Failure
- Symptoms: Loss of power during digging or lifting operations could also point to issues within the hydraulic system. When under load, the excavator may fail to move properly, making the task difficult and inefficient.
- Possible Causes:
- Low hydraulic fluid levels: Insufficient hydraulic fluid can prevent the hydraulic pump from providing enough pressure to operate the boom, arm, and bucket effectively.
- Hydraulic pump failure: A worn-out or failing hydraulic pump can cause a drop in hydraulic pressure, leading to sluggish performance under load.
- Leaking hydraulic lines: Leaks in the hydraulic lines or cylinders can also result in a loss of hydraulic pressure, causing the excavator to struggle under load.
- Low hydraulic fluid levels: Insufficient hydraulic fluid can prevent the hydraulic pump from providing enough pressure to operate the boom, arm, and bucket effectively.
- Symptoms: Loss of power during digging or lifting operations could also point to issues within the hydraulic system. When under load, the excavator may fail to move properly, making the task difficult and inefficient.
- Engine Overheating
- Symptoms: An overheated engine can cause a loss of power under load, as the engine may go into a safety mode to prevent further damage. If the engine temperature rises too high, it can result in power reduction or stalling.
- Possible Causes:
- Low coolant levels: If the coolant level is low, the engine may overheat, especially during demanding operations.
- Faulty radiator or cooling fan: If the radiator is clogged, or the cooling fan is not functioning correctly, the engine may not be able to maintain a safe operating temperature under load.
- Low coolant levels: If the coolant level is low, the engine may overheat, especially during demanding operations.
- Symptoms: An overheated engine can cause a loss of power under load, as the engine may go into a safety mode to prevent further damage. If the engine temperature rises too high, it can result in power reduction or stalling.
- Electrical System Issues
- Symptoms: An issue with the electrical system can prevent the engine from running smoothly under load. Symptoms may include the engine sputtering, stalling, or failing to respond to operator input.
- Possible Causes:
- Weak battery or charging system failure: A failing alternator or weak battery can lead to insufficient power being provided to the engine, especially during heavy load operations when more power is needed.
- Faulty sensors or wiring: Modern excavators, like the John Deere 120, have complex electrical systems. If a sensor fails or if there is a wiring issue, it can result in poor performance.
- Weak battery or charging system failure: A failing alternator or weak battery can lead to insufficient power being provided to the engine, especially during heavy load operations when more power is needed.
- Symptoms: An issue with the electrical system can prevent the engine from running smoothly under load. Symptoms may include the engine sputtering, stalling, or failing to respond to operator input.
- Inspect the Fuel System
- Fuel filter: The first step is to check the fuel filter for any clogs or debris. A clogged filter can restrict fuel flow, especially under load. Replace the fuel filter if it appears dirty or clogged.
- Fuel pump: Check the fuel pump to ensure it is working properly. Low pressure from the fuel pump can prevent the engine from receiving enough fuel under load. Use a fuel pressure gauge to test the fuel system's performance.
- Fuel lines: Inspect the fuel lines for leaks or blockages. Leaking or blocked fuel lines can cause fuel starvation, resulting in loss of power.
- Fuel filter: The first step is to check the fuel filter for any clogs or debris. A clogged filter can restrict fuel flow, especially under load. Replace the fuel filter if it appears dirty or clogged.
- Examine the Air Intake and Exhaust Systems
- Air filter: Check the air filter for dirt and debris. A clogged air filter can prevent the engine from receiving the proper amount of air, leading to reduced power under load.
- Exhaust system: Inspect the exhaust system for blockages. If the exhaust pipe or muffler is clogged, it can cause excessive back pressure and reduce engine performance.
- Air filter: Check the air filter for dirt and debris. A clogged air filter can prevent the engine from receiving the proper amount of air, leading to reduced power under load.
- Inspect the Hydraulic System
- Hydraulic fluid: Check the hydraulic fluid levels and ensure they are within the recommended range. Low fluid levels can reduce the efficiency of the hydraulic system, causing sluggish operation under load.
- Hydraulic pump and lines: Inspect the hydraulic pump for signs of wear or damage. Leaking hydraulic lines or cylinders can result in a loss of pressure, which may cause poor performance when under load.
- Hydraulic fluid: Check the hydraulic fluid levels and ensure they are within the recommended range. Low fluid levels can reduce the efficiency of the hydraulic system, causing sluggish operation under load.
- Check the Cooling System
- Coolant levels: Verify that the coolant levels are within the required range. Low coolant levels can lead to overheating, especially under load.
- Radiator and fan: Inspect the radiator for blockages or leaks. Make sure the cooling fan is working properly and that there is no debris obstructing airflow.
- Coolant levels: Verify that the coolant levels are within the required range. Low coolant levels can lead to overheating, especially under load.
- Test the Electrical System
- Battery and charging system: Test the battery and alternator to ensure they are providing adequate power to the excavator. A weak battery or malfunctioning alternator can cause performance issues under load.
- Wiring and sensors: Inspect the wiring and sensors for any signs of damage or wear. A malfunctioning sensor can lead to incorrect engine performance.
- Battery and charging system: Test the battery and alternator to ensure they are providing adequate power to the excavator. A weak battery or malfunctioning alternator can cause performance issues under load.
- Regularly change the fuel and air filters: To prevent fuel delivery issues and ensure efficient engine performance, replace the fuel and air filters at the recommended intervals.
- Monitor hydraulic fluid levels: Keep an eye on hydraulic fluid levels and inspect the system for leaks regularly to ensure smooth operation.
- Keep the cooling system clean: Regularly clean the radiator and ensure that the cooling fan is functioning properly to prevent overheating.
- Check battery health: Test the battery and charging system periodically to ensure that it is providing sufficient power for the machine's electrical needs.
The John Deere 120 Excavator is a durable and powerful machine, but it can face issues with running under load that can affect productivity. By understanding the common causes of power loss, such as fuel delivery problems, hydraulic issues, overheating, and electrical system malfunctions, operators can troubleshoot and resolve these problems effectively. Regular maintenance, including checking the fuel system, hydraulic components, cooling system, and electrical system, will ensure that the excavator performs reliably, even under demanding conditions.
By addressing these potential issues early and keeping up with preventive maintenance, operators can maximize the lifespan and performance of their equipment, reducing costly downtime and improving overall efficiency on the job site.
