NDDan
Guest
Remove header lift hose from valve. Then remove fitting that that hose hooked to. Under that fitting is a check valve. It is held in place by snap ring. Remove snap ring and then screw a 5_16NF bolt loosely into check valve. Now pull check valve. It won't come hard. Check for missing or badly damaged oring that seals OD of valve to housing. Also see that nothing is stuck under ball of check valve. Next I would remove plug that rate of lower screw screws into. There is a spring and poppet behind that plug. Be sure the spring has not broke and pieces locking the poppet open. You are thinking exactly right and problem has to be in lowering side of valve. Hope you find problem in first two areas. Might have to dig into pilot control under solinoid for sticking armature or problem with needle and or seat. If not that maybe an orfice. I'd have to dig out the ol book to get more accurate after you check the first two things. Good luck