Komatsu PC138US-10 Hydraulic Excavator Overview and No-Start Diagnosis

[MikePhua]

The Komatsu PC138US-10 is a versatile hydraulic excavator widely used for medium-duty excavation, trenching, landscaping, and utility work. It features advanced hydraulic controls, an efficient engine, and compact design ideal for confined space operations.
Key Specifications

• Engine Power: Approximately 97.2 HP (72.5 kW) at 2050 RPM
  
• Operating Weight: Around 15,700 to 17,000 kg (34,500 to 37,500 lbs)
  
• Bucket Capacity: 0.34 to 1.00 cubic meters (0.45 to 1.3 cubic yards)
  
• Hydraulic System: Maximum pressure approx. 34.8 MPa (5,000 psi) in travel circuit; auxiliary flow up to 242 liters/min (64 gallons/min)
  
• Dimensions: Short tail swing radius (~1.5 meters), compact body to work in tight spaces
  
• Cooling System Capacity: About 17.7 liters (4.6 gallons)
  
• Fuel Tank: About 200 liters (52.8 gallons)
  
• Hydraulics Tank: Approx. 69 liters (18.2 gallons)
  

No-Start and No-Crank Diagnostics
When experiencing a no-start/no-crank condition on the Komatsu PC138US-10, troubleshooting involves systematic checking of electrical, fuel, and mechanical systems.
Electrical System Checks

• Inspect battery condition and connections; ensure sufficient voltage (typically 12V system).
  
• Verify ignition switch operation and wiring continuity.
  
• Check starter motor function and associated relays or fuses.
  
• Inspect safety interlocks such as seat switches which may inhibit starting.
  

Fuel System Inspection

• Verify fuel level and quality; contaminated or stale fuel can cause issues.
  
• Check fuel pump and filter for blockages or failure.
  
• Inspect fuel lines and injectors for leaks or clogging.
  

Mechanical Components

• Assess starter motor engagement with the flywheel.
  
• Confirm that engine immobilizers or security devices are not activated.
  
• Examine the condition of the crank sensor and related timing components.
  

Hydraulic and Other Systems

• Although hydraulics do not directly affect cranking, verify that hydraulic interlocks or control modes are not preventing engine start.
  
• Ensure no mechanical binding or excessive engine drag.
  

Troubleshooting Approach

• Begin with battery voltage tests and starter current draw measurements.
  
• Use a diagnostic scanner compatible with Komatsu systems to check for error codes.
  
• Inspect all related wiring harnesses visually and with a multimeter.
  
• Verify fuel delivery directly at injectors if necessary.
  
• Consider input from operators about recent symptoms or maintenance events.
  

Maintenance Tips

• Maintain battery terminals clean and tight.
  
• Regularly replace fuel and air filters.
  
• Keep software and control systems updated as per manufacturer.
  
• Document troubleshooting steps and findings for future reference.
  

Terminology

• No-Start: Engine attempts but fails to fire.
  
• No-Crank: Engine does not turn over when starting.
  
• Safety Interlock: System preventing start to ensure operator safety.
  
• Diagnostic Scanner: Tool reading electronic fault codes from control units.
  
• Crank Sensor: Detects engine crankshaft position for timing.
  

Small Story
A PC138US-10 operator reported a sudden no-crank condition during a cold morning. After checking battery health and connections, a diagnostic scan revealed a faulty seat switch preventing the start sequence. After replacing the switch, the excavator started immediately, emphasizing the importance of verifying safety interlocks in no-start diagnostics.
Summary List

• Engine power ~97 HP; compact dimensions for tight conditions.
  
• No-start/no-crank often linked to battery, starter, ignition switch, or safety interlocks.
  
• Fuel system cleanliness and pump function are crucial.
  
• Diagnostic tools aid electronic system error detection.
  
• Preventive maintenance improves reliability and reduces downtime.
  
• Document all repair steps for consistency.
  

The Komatsu PC138US-10 combines robust mechanics with advanced electronics, requiring a structured troubleshooting approach to swiftly identify and resolve no-start or no-crank incidents ensuring continued machine productivity.