Excavator CAT E336D E330D E336D2 Main Control Valve Assembly (Multi-way Control Valve) 285-1536 285-1540 Common Faults & Troubleshooting Specific action is weak / not working: Stuck spool in that section, spool/sleeve wear causing internal leakage, damaged O-rings. First measure the outlet pressure of that section to diagnose. All actions are weak: Usually caused by insufficient main pump pressure or a failed main Relief Valve pressure setting. Check system pressure first