I have a 52-6FGCU30 forklift that has intermittent hydraulic troubles. Here is the problem: the raise, tilt and sideshift will intermittently stop functioning or move very slowly. Pulling the levers to the max will yield no improvement but when it gets a little more RPMs it will finally surge to full force. It is not a hydraulic supply problem from the pump as I have pulled the high pressure line off and checked that. I can get 1200 pounds easily at an idle before it stalls. I am thinking there is a bypass valve in the main control block that is hanging open that wont supply fluid to the mast function levers. Has anyone else come across this problem? Also, does anyone have access to a hydraulic schematic for this valve? Thanks for any help you can give.