Kobelco 200LC Excavator Startup and Hydraulic Troubleshooting

[MikePhua]

The Kobelco 200LC and Its Global Footprint
The Kobelco SK200LC hydraulic excavator is part of Kobelco’s long-standing SK series, which has earned a reputation for fuel efficiency, smooth operation, and robust structural design. First introduced in the late 1990s and refined through multiple generations, the SK200LC has been deployed in infrastructure, mining, and forestry projects across Asia, North America, and the Middle East. With an operating weight around 20 metric tons and a bucket capacity of 0.8 to 1.2 cubic meters, it balances power and precision for mid-scale excavation.
Kobelco, founded in Japan in 1905, has sold tens of thousands of SK-series machines globally. The SK200LC remains one of its most popular models, especially in regions where reliability and ease of service are prioritized over advanced electronics.
Terminology Annotation

• Deadman Solenoid: A safety valve that disables hydraulic functions unless specific conditions are met.
  
• Starter Relay: An electrical switch that controls current flow to the starter motor.
  
• ECU (Electronic Control Unit): The onboard computer that manages engine and hydraulic functions.
  
• Belly Plate: A protective steel panel mounted under the excavator to shield components from debris and impact.
  

Common Startup Failures and Diagnostic Pathways
A recurring issue with older SK200LC units is failure to start via the ignition key, despite the engine running when jumped directly at the starter. This suggests a fault in the starter relay circuit, safety interlocks, or battery relay system.
Recommended diagnostic steps:

• Check Fuse Integrity: A blown fuse in the key switch circuit can disable the starter relay.
  
• Test Starter Relay Terminals: Terminal 30 should carry fused battery power, terminal 87 connects to the starter, terminal 86 receives signal from the key switch, and terminal 85 is ground. Use a test light or multimeter to confirm voltage and continuity.
  
• Inspect Battery Relay and Heater Relay: These are often mounted near the frame and feed power to the starter. Corrosion or loose terminals can interrupt current flow.
  
• Verify Safety Solenoids: Some models include a starter safety solenoid mounted near the sump. If this solenoid fails, the starter circuit remains open.
  

In one field case, a technician traced the issue to a faulty starter relay with a cracked housing. Replacing the relay restored ignition function and eliminated the need to jump the starter manually.
Hydraulic System Inactivity and Solenoid Checks
Another common problem is complete hydraulic inactivity—no boom, arm, or bucket movement—despite the engine running smoothly. This typically points to a failed deadman solenoid or a broken signal circuit.
Steps to isolate the fault:

• Remove Belly Plate Under Cab: Locate the hydraulic manifold with three solenoids mounted beneath the cab door.
  
• Identify Rear Solenoid: This is usually the deadman solenoid responsible for enabling hydraulic flow.
  
• Check Voltage at Solenoid: With the safety lever down, there should be power at the solenoid terminals.
  
• Manually Activate Solenoid: Push the center button on the solenoid. If hydraulics come alive, the solenoid coil is likely faulty.
  

In one repair, a contractor discovered that the solenoid wire had been pinched during a previous service. Replacing the wire and securing it with a protective sleeve resolved the issue.
Electrical System Complexity and Relay Mapping
The SK200LC uses a network of relays near the ECU to manage startup, hydraulic activation, and monitoring. These relays are often unlabeled, making troubleshooting difficult without a schematic.
Best practices:

• Label Relays During Inspection: Use colored tape or tags to identify starter, battery, and safety relays.
  
• Keep a Printed Wiring Diagram: Highlight key circuits such as starter control, hydraulic enable, and ECU power.
  
• Use a Relay Tester: Confirm function before replacement—some relays fail intermittently under load.
  

In one case, a technician used a relay tester to identify a weak coil in the starter relay that passed bench tests but failed under vibration. Replacing it restored consistent startup.
Preventative Measures and Operator Tips
To avoid future electrical and hydraulic failures:

• Inspect belly plates and wiring harnesses quarterly
  
• Replace relays every 2,000 hours or during major service
  
• Use dielectric grease on all connectors exposed to moisture
  
• Train operators to recognize early signs of solenoid failure
  
• Keep spare relays and fuses in the cab for field replacement
  

In a remote forestry operation in British Columbia, a fleet manager implemented a relay rotation schedule and reduced startup failures by 80% over six months.
Conclusion
The Kobelco SK200LC excavator is a durable and capable machine, but like all aging equipment, it requires methodical troubleshooting and proactive maintenance. Startup issues and hydraulic inactivity are often rooted in relay faults, solenoid failures, or wiring degradation. By understanding the electrical architecture and hydraulic interlocks, technicians can restore full functionality and extend the life of these machines. In the field, precision diagnostics and preventative care are the difference between downtime and dependable performance.