How to resolve the issue of slow operation in the Doosan DH220-V—a problem that becomes particularly pronounced when the machine is under load.

 Inspection procedure: 

 

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1. Check pilot pressure: The pilot pressure measured at the gear pump is 40 bar. 

2. Check negative control pressure: The pressure is 40 bar with the control levers in the neutral position and drops to 7–8 bar during operation; this indicates that the valve spools are functioning correctly. 

 

Doosan DMS-5 Diagnostic Software with Troubleshooting v53.3.1 (07.2026)

3. Measure main pump pressures (front and rear): The relief pressure measured at the main pump test ports is 250 bar, and the system fails to boost pressure (normal relief pressure is 330 bar); this indicates abnormal pressure requiring adjustment. 

4. Adjust the main relief valve: Tightening the 350-bar adjustment nut by one full turn resulted in no change in pressure; this indicates a fault in the main relief valve. 

 5. Remove, clean, and reassemble the main relief valve.

 Cause: Impurities inside the main relief valve prevented the poppet from resetting, causing internal leakage during operation.

 

06.2023 Doosan e-Doctor 2.4.0.7 Diagnostic Software

Remedy: After cleaning and repair, adjust the pressure to the normal operating level; the machine then operates correctly. First, adjust the maximum pressure to 350 bar, then adjust the setting to 330 bar. 

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