Short Answer: Slow excavator movement is often caused by hydraulic system issues, engine power loss, mechanical wear, or electrical faults. A systematic check of hydraulic fluid, filters, engine performance, and sensors is required for diagnosis.
Detailed Troubleshooting Guide
1. Hydraulic System Problems (Most Common Cause)
Low or Contaminated Hydraulic Fluid:
Cause: Hydraulic fluid is the lifeblood of the system. Low fluid level or dirty fluid (containing metal particles, water, or air) reduces pump efficiency and causes slow, sluggish operation.
Solution: Check the fluid level on the dipstick. If the fluid is dark, milky, or has a burnt smell, drain and replace it. Change the hydraulic filters regularly (recommended every 2,000 hours).
Worn Hydraulic Pump:
Cause: Internal components (e.g., pistons, swashplate) wear over time, causing internal leakage and a drop in system pressure and flow.
Solution: Test the system pressure with a gauge. If it's below the manufacturer's specification (e.g., main pump pressure below 300 bar/4,350 psi), the pump may need repair or replacement.
Faulty Relief Valve:
Cause: A stuck or weak relief valve can cause the system to bleed off pressure prematurely, resulting in low overall power.
Solution: Clean, test, or replace the relief valve and reset the pressure to the standard setting.
Clogged or Leaking Hydraulic Lines:
Cause: Restricted or leaking hoses and tubes reduce flow to the cylinders and motors.
Solution: Inspect all lines for kinks, crushing, or leaks. Replace any damaged components.
2. Power System Issues
Insufficient Engine Power:
Cause: The engine must provide adequate RPM and torque to drive the hydraulic pump. Low RPM, a clogged air filter, poor fuel quality, or a leaking turbocharger can all lead to power loss.
Solution: Check and maintain engine RPM. Inspect and replace the air, fuel, and oil filters as scheduled.
Fuel Injection Problems:
Cause: A failing fuel pump or clogged/dirty injectors result in poor combustion and reduced engine power.
Solution: Test fuel pump pressure and have the injectors serviced or replaced.
3. Mechanical Component Wear
Worn Swing Bearing or Gear:
Cause: Excessive clearance in the swing bearing or worn gears can cause slow and jerky rotation.
Solution: Check for unusual noises and measure gear backlash. Replace components if wear exceeds limits.
Travel Reduction Gear Damage:
Cause: Internal damage to the travel motor's reduction gear leads to slow travel speed and loss of power.
Solution: Disassemble and inspect the travel motor and gearbox for worn gears or bearings.
4. Electrical System Faults
Faulty Sensors:
Cause: Incorrect signals from sensors (e.g., pressure, speed) can cause the machine's controller (ECU) to derate the engine or hydraulics.
Solution: Use a diagnostic tool to read error codes and check sensor connections and functionality.
Solenoid Valve Failure:
Cause: A burned-out solenoid coil on a control valve will prevent the valve spool from shifting, disabling that specific function.
Solution: Test the solenoid's resistance with a multimeter and replace it if it's out of specification.
Proactive Maintenance Tips
Check hydraulic fluid level and condition daily.
Change hydraulic and engine filters according to the service schedule.
Clean the hydraulic oil cooler and radiator every 500 hours to prevent overheating.
Perform a full engine service (filters, valve clearance) every 2,000 hours.
When troubleshooting, always start with the hydraulic system before moving to the engine and mechanical components.