Hi. I am new to this forum and I need help. I have a 2008 Massey Ferguson 2625 four wheel drive tractor with independent PTO. When I turn the PTO on, the 3-point lift arms stops working. It has a new Hydraulic filter, and new oil. I am getting 2350 lbs. of pressure at 3-point lift arms test port. As soon as I turn the PTO on, the pressure falls to zero. I pulled the hydraulic lift cover off and I put the cap and stand pipe back on, I started the tractor to check to see if I had any leaks around the o rings, on the pipe but did not see any leaks, I had a good flow of oil came out of the stand pipe that feeds the 3-point lift arms and soon as I turned the PTO on, the oil from the stand pipe stopped and when I turned the PTO off the oil comes back through the stand pipe. Also the priority valve(part #2749A00401) has a open hole with a t stamped on it. I am wondering if a plug or something goes in that open hole. I nor anyone else cannot find any pictures of the priority valve to see if anything is missing. I've talked to several Massey dealerships and a service rep and they all told me they have never heard of this before. Does anyone have any ideas?