I have a small power pack that I use in my concrete boom pump business. The high flow, low pressure circuit dumps to tank at 44 bar and the low flow, high pressure circuit dumps to tank at 240 bar. When I fire up the unit and dead-head it, the pressure first goes to 240 bar, then oscillates a few times between 240 bar and 44 bar, and then it settles in at 44 bar. I can raise the pressure setting on the high flow, low pressure circuit to around 100 bar before it stalls the honda engine, though this makes the unit barely useful. This tells me that the low pressure circuit is healthy. I thought it might be the check valve, but I have never seen them oscillate. Don't understand how the pressure relief valve would fail in an oscillatory manner either. I am hoping the forum can help me figure out what might be going on. The hydraulic schematic for the valve is attached. Any ideas what would cause this behavior?
I wonder if there is some debris holding open that check valve in the center causing the high pressure to escape to the lower relief? Just something easy to check first.
that was my first thought, but I could not rationalize the oscillatory behavior if that was the issue. I'll tear it down soon and advise back. Thank you for your comment
Could be chattering or misadjusted setting.