I am working on a 1996 SPX that has been sitting for awhile but is in excellent shape. I changed all fuel lines, oil lines, selector switch and a new rotary valve. I primed the oil pump line and the small injection lines. All lines were full and oil all the way to the oil injection fitting. After sitting a day or two, i noticed that the PTO side injection line was empty. Do the injection fittings have a check valve? Can you replace the fitting or do you have to replace the rotary valve cover? Any help is appreciated!!