Having some hydraulic issues with my 490e later serial #. Pilot pump and all hydraulic filters are new. pilot relief and regulated pressure is 720-730 ish and 510-520 ish tested as the book says to. The main problem im having is the hydraulics are jittery when feathering the controls and swing but running controls full bore the hydraulics run smooth for the most part, engine rpm doesnt make it better or worse. The second issue im having is the pump will randomly go short stroke and the hydraulics will be weak then switch to full stroke and stall engine. PVC is showing code 36 which says is arm in pressure switch disconnected, could that pressure switch be the culprit or am I facing several issues? Any help is appreciated! Thanks
I would not ignore that code 36. I would first check the arm-in pressure switch, connector, and wiring before chasing bigger hydraulic parts. The jumpy feathering makes me think there may be a pilot/control side issue too, not only pump stroke.
Working on addressing the arm in pressure sensor now, but apparently thats the one sensor my book doesnt say how to test... I believe the jumpy feathering is in the pilot system, however, when it stutters theres a hiss from the valve block like its pushing past a relief valve, it does this on all the controls as well as swing.... its hard to diagnose the pump stroke issue when it only acts up occasionally so mainly just focusing on the stuttering for now
Screenshot below is wire harness test procedure from a Hitachi EX120-3 manual. If the wire harness tests good, back probe arm in sensor terminals #2 and #3. With controls in neutral sensor output should be approx .60v , and with arm in over releif should be approx 4.50v. The arm in pressure sensor and the pump discharge pressure sensor are the same. As a last resort you could swap them as a test.
Very helpful thank you, I'll check it out tonight and come back with results
Tested the arm in pressure sensor and found it to be a bad sensor. Replaced sensor and code 36 on PVC went away but made no difference in operation. Controls are still jittery when feathering and I have noticed a hissing from the main valve block when the hydraulics stutter like its pushing past a relief valve or closing control valve... also found when putting the work mode in precision the arm out function full speed is very shaky