Parked my hitachi uh122 last year everything was working fine. Removed the 3 main control valve to reseal due to excessive leaking Reinstalled the valve changed all filters drained the old oil and put back new oil Result: No pressure or very low pressure Checked the relief valve (seems to operate well (up and down) Check and cleaned the overload pressure valve. Disassemble the whole thing again to check the poppet in the close center spools - looks ok Here's where I'm heading now: I'd like to test the pressure of the relief valve since I have changed the o-ring but there's no xtra port to plug a gauge and adjust the valves. is there any other place I can plug in? Every port of the control valve are connected with metal piping... Another question: Should I pursue investigating relief valves or do you have another idea? thank A few thing I did to troubleshoot before dismantling: I tried to troubleshoot the main boom first. Raise boom Xtra high use all 3 control valves and push into 1 metal pipe through a slow return to the cylinder hoses - No movement. I have remove the hoses from the circuit coming from the top cylinder - started the machine again, main control valve at neutral position and oil was coming from the return circuit?? I then plug the return circuit leaving the top cylinder open hoping to eliminate the "Air lock" theory. pulled on the raise boom - Nothing happened. Any help?
Good day suggest you begin at the beginning check the pilot pressure kind regards Uffex