2004 Jinma 224 with loader(it is in his profile)
IF the loader and power steering are working, then you have flow from the pump. I think if it was an "O" ring, it would at least try and lift the arms without an impliment, but it wouldn't stay up if any weight was applied to the arms. What is the status of the 3PH speed control valve located in front of the seat? Is it fully clockwise(closed) or fully counterclockwise(open)? On some of the Jinmas, that valve knob has two functions.
1. Regulates downward speed of a heavy 3PH impliment.
2. When fully closed the valve restricts the flow into the 3PH cylinder completely and sends the pressure instead to a rear remote port to allow the control of a remote single acting cylinder such as in a dump trailer. With the valve knob closed, the 3PH arms won't move.