D15 hitch control valve

I bought a cheap loader for my d15, and got it put on, but what i found is that i can't lower the loader without first lowering the rear blade. I thought that the knob on the outlet on the rear of the tractor was supposed to hold the rear hitch up. It doesn't do anything, threaded in or out. Was i wrong, or do i have something not working right inside that valve? I was planning on selling it this fall as a complete setup for someone to clear snow, but as it sits, its kind of a useless setup.

The loader can be disabled, by installing a simple gate valve, in the single line,  that goes to the 2 loader cylinders.  Tractor hydraulics are just doing what they were designed to do.  that means lift arms lift first, then the remote cyl lifts.  On the drop, the remote drops first, then the lift arms drop. System was designed for plows or discs, loader, not so much...