The hose you loosened is a low pressure line. It carries fluid from the transmission pump to the main pump. If you have pressure in that line, you should have sufficient oil being supplied to the main pump to function. If the small reservoir above the pump is full, the transmission pump is supplying sufficient oil. I am guessing you have a problem with the stroke control valve in the main pump, or a failure of the main pump. arts in item 27 is the stroke control valve. Loosen nut 25 and then screw out #26 to remove the stroke control valve assembly. The top 2 parts have tapered seats that mate together. The top most part(valve seat) will not come out when you remove the plug. You need to remove the top plug and drive it out with a punch from the top. Before you do that however, inspect the tapered seat on the valve just below it. If the tapered seat looks good with no gouges, dents, cracks or debris, then the seat is probably ok also and does not need to be removed. If everything looks good, clean all the parts and reassemble. Sometimes a small piece of debris gets between the valve and seat, not allowing pump to build pressure. Of course adjusting this valve using a pressure gauge is what sets pump pressure.
