I've got an '81 Ford 1900, and the 3 point hitch is weak, it will lift most of my implements, but nothing more than about 400 lbs. I have replaced the 3 point lift cylinder seals, flushed and replaced all the hydraulic fluid, cleaned the hydraulic filter, and now I have replaced the hydraulic pump itself, but it's still not even strong enough to lift a friend(200lbs) standing on my box blade. I pulled all the relief valves out of it last night and they're all in good condition. Hydraulic fluid is new and not low. I'm stumped, hopefully somebody on here can help me! It's got to be some sort of bypass somewhere on this thing stuck open.