Troubleshooting Starting Issues on a Kobelco SK120 LC Excavator (1992 Model)

When a machine like the Kobelco SK120 LC, a 1992 model, refuses to start, it can cause significant downtime on construction sites or during excavation projects. The Kobelco SK120 LC, a popular mid-sized hydraulic excavator, is known for its reliability and performance. However, like any heavy machinery, it can experience issues with starting, and identifying the root cause can be tricky. In this article, we’ll explore the common causes for starting problems, delve into troubleshooting steps, and provide potential solutions that could help operators get their equipment back in working order.

Understanding the Kobelco SK120 LC

Before diving into the troubleshooting process, it's important to understand the features and specifications of the Kobelco SK120 LC.

The Kobelco SK120 LC is part of Kobelco's line of crawler excavators, which are known for their power, stability, and fuel efficiency. The 120-ton model was designed for various digging and lifting applications and has a strong reputation in the construction and mining sectors. Key features include:

Engine Type: Typically powered by a 4-cylinder or 6-cylinder diesel engine (depending on the specific variant).
Operating Weight: Approximately 12,000 to 13,000 kg, making it versatile for various job sites.
Hydraulic System: Offers a high-flow hydraulic system for efficient digging, lifting, and other tasks.
Track System: Crawler tracks ensure good stability on rough or uneven terrain.

Despite its solid engineering, like any piece of machinery, the Kobelco SK120 LC can face issues related to the starting system, which can stem from several possible causes.

Common Causes for Starting Failures

When a Kobelco SK120 LC fails to start, it could be caused by a variety of mechanical or electrical issues. Here are some of the most common culprits:

1. Battery Issues

Problem: The most common cause for a starting failure is a dead or weak battery. Over time, batteries degrade and may fail to supply enough power to start the engine.
Symptoms: If the starter motor turns slowly or there is no power at all when turning the key, it’s often an indication of a battery issue.

2. Fuel Delivery Problems

Problem: If fuel isn't reaching the engine, the machine won’t start. This could be caused by a clogged fuel filter, air in the fuel lines, or a faulty fuel pump.
Symptoms: The engine may crank but not start, or it may start and stall immediately.

3. Starter Motor Failure

Problem: The starter motor is responsible for cranking the engine. If it fails, the engine will not turn over.
Symptoms: A clicking sound when attempting to start or no sound at all can indicate a starter motor issue.

4. Electrical Issues

Problem: Electrical connections are critical to the starting process. Loose or corroded battery terminals, damaged fuses, or faulty relays can prevent the engine from starting.
Symptoms: Dim lights, erratic electrical behavior, or no response when attempting to start the machine may point to electrical issues.

5. Glow Plug Failure

Problem: In colder climates, glow plugs are used to preheat the engine before starting. If one or more glow plugs fail, the engine may struggle to start, particularly in cold conditions.
Symptoms: Extended cranking times or difficulty starting in cold weather.

6. Ignition Switch Problems

Problem: A malfunctioning ignition switch may not send the proper signal to engage the starter motor or fuel system.
Symptoms: Turning the key has no response, or the machine won’t even attempt to start.

Troubleshooting the Kobelco SK120 LC

If your Kobelco SK120 LC won’t start, here’s a step-by-step guide to troubleshoot the issue:

1. Check the Battery

Action: Inspect the battery for corrosion, loose connections, or any signs of wear. If necessary, charge the battery or replace it with a new one.
Test: Use a multimeter to check the voltage. A fully charged battery should read around 12.6 volts.

2. Inspect the Fuel System

Fuel Lines: Check for any blockages, leaks, or air pockets in the fuel lines. If the fuel filter is dirty, replace it.
Fuel Tank: Ensure there is enough fuel in the tank and that it hasn’t gone stale or contaminated.
Fuel Pump: If you hear a whining noise or notice a lack of fuel pressure, the fuel pump might need replacement.

3. Examine the Starter Motor

Visual Inspection: Check the wiring to the starter motor. Make sure all connections are tight and free of corrosion.
Test the Starter: If the starter motor shows signs of wear (such as excessive noise), it may need to be replaced.

4. Check the Electrical System

Inspect Fuses and Relays: A blown fuse or faulty relay can prevent the system from powering up. Replace any blown fuses and test the relays for functionality.
Battery Terminals: Clean the battery terminals to ensure good contact. Corroded terminals are a common cause of starting issues.

5. Test the Glow Plugs

Action: In colder weather, inspect the glow plugs and verify they’re operating properly. If the glow plugs aren’t functioning, they should be replaced.
Testing: Use a multimeter to check for proper resistance across the glow plug terminals. If the resistance is too high, the glow plug may be faulty.

6. Check the Ignition Switch

Action: Test the ignition switch to ensure it’s sending the correct signal to start the engine. A multimeter can be used to check for continuity when the key is turned to the "start" position.
Replacement: If the ignition switch is faulty, it should be replaced.

Real-Life Case: Kobelco SK120 LC Starting Issue

A construction company operating a fleet of heavy machinery encountered starting issues with one of their Kobelco SK120 LC excavators. The machine would crank but not start, and they were unsure of the cause. After performing a basic inspection, they discovered that the fuel filter had become clogged with debris, preventing the proper flow of fuel to the engine.

Once the fuel filter was replaced and the fuel lines cleared, the excavator started up without issue. The company was able to avoid costly downtime, saving both time and money by addressing the problem before it escalated into a more severe issue.

Preventive Maintenance Tips

To prevent future starting issues with your Kobelco SK120 LC, consider the following preventive maintenance practices:

Regularly inspect the battery for corrosion and clean connections.
Replace fuel filters at the recommended intervals to prevent fuel system clogs.
Inspect electrical components periodically to ensure all connections are secure and free of corrosion.
Check glow plugs before winter months to ensure smooth cold starts.
Service the starter motor and ignition system to ensure reliable performance.

Conclusion: Ensuring Long-Term Reliability of Your Kobelco SK120 LC

Troubleshooting starting issues on a Kobelco SK120 LC can often be resolved with basic inspections and maintenance. By following a systematic approach and checking key components like the battery, fuel system, starter motor, and electrical connections, operators can ensure that their machine starts reliably and performs at its best.

Preventive maintenance is key to avoiding costly repairs and extending the life of your Kobelco SK120 LC. Regular checks and prompt attention to minor issues can save both time and money, allowing you to keep your equipment running smoothly on the job site.