Doosan DL06 & DL08 Common Rail Fuel System – Complete Technical Guide

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DL06 & DL08 Common Rail Fuel System – Complete Technician-Level Guide This guide explains the Common Rail fuel system used on Doosan DL06 and DL08 diesel engines. It combines the system layout diagram and the detailed fuel schematic drawing to show fuel flow, pressure zones, electronic control, and common failure modes. This is written for technicians who want a clear, step-by-step understanding of how the system works and how to diagnose faults. 1. Common Rail System Overview (DL06 & DL08) The Common Rail system separates fuel pressurization from injection timing . Instead of one mechanical pump sending fuel directly to each injector, a high-pressure pump feeds a shared rail , and electronically controlled injectors perform precise injection based on commands from the ECU (Control Unit) . Low-pressure side (black lines): draws fuel from the tank, filters it, and supplies the high-pressure pump. High-pressure side (red lines): compresses fuel an...
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Doosan DX225 Bucket Slow or Weak: Hydraulic Pressure & Repair Guide

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Doosan DX225 Bucket Slow or Weak – Technician-Level Troubleshooting Guide

Doosan DX225 excavator bucket cylinder troubleshooting and hydraulic pressure testing points.
This guide explains the hydraulic causes and technician-level troubleshooting steps for a bucket slow or weak condition on the Doosan DX225 / DX225LC hydraulic excavator.

Test PointPressure SpecificationAdjustment Method
Pilot Pump Outlet40 ± 5 barRegulator Screw
Main Pump (Stall)330 barMain Relief Valve
Power Boost350 barSolenoid Logic
Joystick Signal23.5 ± 1.5 barPilot Valve


1. Bucket Hydraulic System Overview

  • Main hydraulic pumps (P1 / P2)
  • Pilot control system
  • Main control valve bucket section
  • Bucket cylinder
  • Power mode / power boost logic
  • Priority and LS circuits

2. Required Tools and Conditions

  • 600 bar pressure gauge
  • Pilot pressure gauge (0–60 bar)
  • Flow meter
  • Thermometer
  • Two technicians
  • PPE (gloves, eye protection)

3. Safety Precautions

  • Park on level ground
  • Warm hydraulic oil to operating temperature
  • Clear the working area
  • Use two people during pressure tests
  • Follow manufacturer safety rules

4. Hydraulic Pressure Specifications

4.1 Pilot Pressure

  • Pilot pump outlet: 40 ± 5 bar
  • Joystick pilot line: 23.5 ± 1.5 bar

Adjustment: Turn screw clockwise to increase, counterclockwise to decrease.

4.2 Main Pump Pressures (Power Mode)

Condition Main Pressure Pilot Pressure
Neutral 20–40 bar 30 bar +10 bar
Cylinder Stall 330 bar +5 bar 30 bar +10 bar
Stall + Power Boost 350 bar +10 bar 30 bar +10 bar

4.3 Swing Priority Valve

  • Digging mode: 0 bar
  • Trenching mode: 20–40 bar

5. Step-by-Step Troubleshooting

Step 1 – Check Pilot Pressure

  • Normal: 23.5 ± 1.5 bar
  • If low: adjust regulator, clean pilot filter, check leaks

Step 2 – Check Main Pump Pressure

  • Normal stall: 330 bar
  • Power boost: 350 bar
  • If low: adjust pump regulator, check relief valve, inspect pump

Step 3 – Check Bucket Control Valve

  • Spool sticking
  • Internal leakage
  • Weak relief valve
  • Regen valve stuck

Step 4 – Check Bucket Cylinder

  • Rod seal leakage
  • Internal bypass
  • Scoring inside cylinder

Step 5 – Check Flow & LS Circuit

  • Use flow meter if pressure is correct but bucket is slow
  • Check LS line
  • Check swing priority valve

6. Common Causes & Fixes

  • Low pilot pressure → adjust regulator
  • Low main pressure → adjust pump, check relief valve
  • Valve leakage → clean or overhaul
  • Cylinder bypass → rebuild cylinder
  • LS signal issue → repair LS line

7. Technician Notes

  • Always test with warm oil
  • Check pilot pressure first
  • Use flow meter for pump adjustments
  • Document all readings
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