Kobelco SK-220 Performance Issues: Troubleshooting the Revolutions Sender

[MikePhua]

Introduction to the Kobelco SK-220
The Kobelco SK-220 is a popular mid-range hydraulic excavator that is known for its reliability, efficiency, and powerful performance in various industries such as construction, mining, and demolition. Part of Kobelco's SK series, the SK-220 has been widely recognized for its fuel-efficient engines, ease of maintenance, and advanced hydraulic systems. However, like any heavy machinery, the SK-220 can encounter performance issues that need to be addressed promptly to avoid costly downtime.
One common issue faced by owners and operators of the Kobelco SK-220 is the lack of acceleration under load. This problem can lead to poor performance, affecting the machine’s productivity. In many cases, the root cause of this issue is related to the revolutions sender, which plays a vital role in the engine's performance and response under load.
Understanding the Revolutions Sender
The revolutions sender, also known as the engine speed sensor, is a critical component in modern heavy equipment, including the Kobelco SK-220. It measures the engine’s RPM (revolutions per minute) and sends this data to the machine’s control system, which adjusts various engine parameters such as fuel delivery and exhaust gas recirculation. The sensor ensures that the engine operates efficiently under different load conditions and helps the machine maintain optimal performance.
In some cases, when the revolutions sender is malfunctioning or providing incorrect readings, it can lead to problems like a lack of acceleration under load, stalling, or reduced engine power. The sensor’s failure may not only cause operational issues but can also affect the machine’s overall fuel efficiency and increase wear on critical engine components.
Symptoms of a Faulty Revolutions Sender
When the revolutions sender fails or starts malfunctioning, the operator may notice several signs that indicate there is an issue with the engine’s performance:

1. Lack of Acceleration Under Load:
   One of the most common symptoms of a faulty revolutions sender is the inability of the machine to accelerate properly when under load. This can cause the excavator to feel sluggish or struggle to lift heavy materials.
   
2. Erratic Engine Speed:
   The engine may rev erratically or have inconsistent speeds, especially during heavy lifting or digging operations. This may be a result of incorrect feedback from the revolutions sender.
   
3. Reduced Power Output:
   If the sensor is malfunctioning, the machine may experience reduced power output, making it difficult to perform tasks efficiently, especially in demanding conditions.
   
4. Engine Stalling:
   In some cases, a faulty revolutions sender can cause the engine to stall, particularly when the excavator is under load or during operation in high-stress environments.
   

Troubleshooting the Revolutions Sender Issue
If you are experiencing performance issues with your Kobelco SK-220 and suspect the revolutions sender is the problem, there are a few troubleshooting steps you can take to diagnose and resolve the issue.

1. Check the Revolutions Sender Wiring and Connections:
   Start by inspecting the wiring and connections leading to the revolutions sender. Over time, wires can become frayed, corroded, or disconnected, leading to incorrect readings. Ensure all connections are secure and free of any visible damage.
   
2. Inspect the Revolutions Sender Itself:
   The sender itself may become worn out or damaged due to continuous exposure to vibrations and heat. Check the sensor for any signs of physical damage, such as cracks, burn marks, or excessive wear. If the sender looks damaged or dirty, cleaning or replacing the part may be necessary.
   
3. Test the Sensor’s Output:
   Use a multimeter to check the output from the revolutions sender. By measuring the voltage or resistance, you can determine whether the sensor is providing accurate data. Consult the Kobelco SK-220’s service manual for the exact specifications for the revolutions sender’s output.
   
4. Check the Machine’s ECU and Control System:
   If the sensor appears to be functioning correctly, the issue may lie within the excavator’s control system. The ECU (Electronic Control Unit) is responsible for interpreting the data sent by the revolutions sender and adjusting the engine parameters accordingly. A malfunction in the ECU may result in improper power delivery to the engine.
   
5. Look for Fault Codes:
   Modern machines like the Kobelco SK-220 are equipped with diagnostic systems that can provide fault codes to help pinpoint the source of the issue. Check the onboard diagnostics for any error codes related to the engine speed sensor or the overall engine performance.
   

Replacing the Revolutions Sender
If the revolutions sender is found to be faulty and no simple fixes are possible, replacement may be necessary. Replacing the sender is a relatively straightforward process, but it requires care and attention to ensure proper installation. Here’s a general guide for replacing the revolutions sender:

1. Disconnect the Battery:
   Before working on any electrical components, disconnect the battery to avoid any electrical shock or damage.
   
2. Locate the Revolutions Sender:
   The revolutions sender is typically located near the engine, often attached to the crankshaft or flywheel. Refer to the service manual for the exact location on your specific model.
   
3. Remove the Faulty Sender:
   Carefully disconnect the wiring and remove the old revolutions sender. Be cautious not to damage any surrounding components during the removal process.
   
4. Install the New Sender:
   Install the new revolutions sender in the same position as the old one, ensuring all connections are secure. Reconnect the wiring, double-checking that everything is in place.
   
5. Test the System:
   Once the new sender is installed, reconnect the battery and start the machine. Monitor the engine performance to ensure that the issue has been resolved and that the excavator accelerates smoothly under load.
   

Preventative Measures and Maintenance Tips
To avoid future issues with the revolutions sender and to ensure the longevity of your Kobelco SK-220, regular maintenance is crucial. Here are some preventative measures and tips for keeping the machine running smoothly:

1. Routine Inspections:
   Regularly inspect the revolutions sender and its connections as part of your machine’s routine maintenance. Look for signs of wear or damage that could lead to performance issues.
   
2. Keep the Engine Clean:
   Regularly clean the engine area to prevent dirt, debris, and dust from accumulating around the revolutions sender and other sensitive components. This can help extend the life of the parts and ensure accurate performance.
   
3. Monitor for Warning Signs:
   Keep an eye out for any changes in engine performance, such as poor acceleration, erratic speeds, or reduced power. Early detection of issues can prevent more significant problems down the road.
   
4. Follow Manufacturer Recommendations:
   Always follow the manufacturer’s maintenance schedule for oil changes, air filters, and other engine components. Proper maintenance of the entire engine system can help prevent issues with the revolutions sender and other critical parts.
   

Conclusion
The revolutions sender plays a vital role in maintaining the engine’s performance on the Kobelco SK-220 excavator. When this component malfunctions, it can cause a variety of problems, including lack of acceleration, reduced power, and stalling. Troubleshooting and addressing issues with the revolutions sender promptly can help restore the machine’s efficiency and prevent costly downtime. By understanding the causes, symptoms, and maintenance tips for the revolutions sender, operators can ensure the long-term performance and reliability of their Kobelco SK-220.