I have installed new hyd pump and piston seals, I do not have any pressure at the test port unless I apply a load to the three point hitch arms. I have hooked it to a load that it can't lift and I can get 1600 lbs on the guage, then I hooked it to a 12ft pull type mower and it will lift the front of the mower, but it set there and cycles as if the draft control is working and the pressure guage jumps between 100 and 700 lbs. Have also changed to different internal cylinder and control vavle same results. Any ideas ?