daniel790d
Member
Hey guys. So I'm trying to diagnose a differential pressure issue on a year 2000 Pettibone 10044. My service manual tells me to: 1. Bottom out the differential pressure adjustment on the main control valve bank. 2. Adjust the differential pressure on the pump, down to 625 psi initially, then 3. adjust the D.P on the main valve down to 600, and finally set the D.P on the pump down to 500 psi, which is to be my actual standby value. The problem is, when I try to make these adjustments and bottom out the screw on the main valve initially, then crawl under to the pump's differential control, I find that I cannot get the pressure to come below 1000 psi. With the machine idle and no functions being actuated, my load sense reading is 0, so I have to rule out the problem as being a stray load signal, right? I would say it's the control spring for the pump D.P adjustment, but the pump is a reman that I just installed, and I had the same problem on the old pump (I replaced it because it had cavitated and was only pumping out about 1/3 of its rated gpm). It can still carry out all its functions normally, except that it's making low steering pressure, which I think is an isolated issue, but it does have its quirks, and I wonder if that can be attributed to not being able to properly adjust the system. So basically besides that I'm just burning a bit more fuel with the pump being on stroke all the time, but it still irks me.