If you are using the tractor's hydraulic pump to run the BH, why are you using a hydraulic resovoir tank on the BH? I would say if it has it's own tank, it is probably plummed to be using it's own(PTO driven) hydraulic pump. Due to the demands of a BH, most have their own pumps and do not even connect into the tractors hydraulics.
If you are using the tractor hydraulic pump I would say it should be plummed as follows. From the High pressure quick connect(Female) on the back of the tractor, A male connector plugs into this fitting and runs via hose to the inlet port on the gang of BH spool valves. The return port from this gang of valves flows through a hose with a female connector on the end that plugs onto the male quick connect return fitting on the rear of the tractor, which runs back into the right rear corner of the tractors hydraulic resovoir.
From what I have gathered studying my system, rear hydraulics seem to have been a afterthought on the Jinma. The pressure supplied to that rear pressure quick connect is the same pressure supplied from the 3point hitch hydraulic control valve to the 3PH lift cylinder. The only difference is the pressure going/comming from the 3PH cylinder goes through the lowering speed regulating valve located in front of the seat. In order to apply pressure to that quick connect, you must have the 3PH control in the "Raise" position. To keep the 3PH cylinder from raising the arms at the same time and the control linkage that is attached to the right arm from bumping the 3ph control lever back to "neutral" when the arms reach the top, you must fully close the 3PH speed/rate control knob in front of the seat(turn fully clockwise, be sure and loosen the locking setscrew first). This will prevent fluid from being sent to the 3PH cylinder and the arms will not try and raise. With the control knob screwed closed, all the pressure/flow will be sent to that rear female quick connect fitting.
My plain 284 only has the pressure fitting, it dosn't have a return fitting like the LE models do. I think mine was intended to operate a single acting cylinder on a dump trailer. With the rate knob in front of the seat closed, a dump trailer could be raised and lowered with the 3PH control lever.
