AC WD Hydraulic System

I have a 1949 Allis Chalmers WD. My problem is with the hydraulic system. The original Hydraulic pump was bad. I bought a used replacement off EBay. The purchased pump is in excellent condition and looks like recently rebuilt. It came with the top valve, also looking in good condition. The replacement pump was installed and I used the valve that came with replacement pump. The problem i have is that as soon as the engine is started, the lift cylinders go up to their upper limit, regardless of the position of the lift lever or valve setting They lock and cannot be pulled down so obviously there is no path for the hydraulic fluid to flow in the opposite direction. I have 3 manuals plus the internet and nothing talks about this problem. There is plenty of information about the various settings and adjustments for the 3 modes of draft control and I've experimented with all of those but nothing I've done has any effect on the hydraulically locked lift arms. I'm looking for an old farmer or an old tractor repairman who can help me. These AC tractors have one way lift cylinders and utilize a single hydraulic line between the pump valve and the cylinders. So, the hydraulic fluid needs to be able to flow in both directions through that single line. Mine flows out but it doesn't flow back, as if there was a check-valve stopping the return. I installed all the replacement parts in exactly the same way as the original so nothing should have changed. SUGGESTIONS?

With the hand lever fully DOWN, turn in screw "D" all the way in. Leave it there and start the engine to see if the lifting problem stops. Then, with the hand lever fully DOWN screw out screw "D" and see what happens. But first, do you have the Traction Booster linkage from the drawbar spring yoke connected ??????? Screw "A" needs to be turned "IN" into the divot on the pumps side to disable the Traction Booster system, which will cause the pump to continuously lift and never lower.

Dr A
Thank you for your response. It sounds like I've found that valuable resource I was seeking. I hope you don't mind if I continue to pick your brain with follow-up questions.
The tractor in question is almost exclusively used with a 5' brush mower to keep fields clear around a rural property we own.
In our attempts to get hydraulics working again, we did have a manual that explained the various adjustment screws and I'm sure we had screw D all the way in and out several times and it didn't fix the problem. In your reply, I see something that may be the next thing to investigate. You put emphasis on asking if we had the Traction Booster linkage from the drawbar spring yoke connected. In fact, we do not. It's there but currently hanging down. We were thinking all we wanted the hydraulics to do was raise the mower for transport and so that linkage was not something to worry about right now. It sounds like it needs to be in the loop but nothing in the manual mentioned that or why. I hope you can explain what that does. It would be great if the solution would be that simple.
The property with the tractor on it is about 3 hours away from my home. We will be spending a week there around Memorial Day so I won't have a chance to go hands-on until then but I'll take any advice you have on procedure, order of operations, testing and adjusting (or links to good information on these). Thanks again for your help

(quoted from post at 10:33:38 03/23/23) Dr A
Thank you for your response. It sounds like I've found that valuable resource I was seeking. I hope you don't mind if I continue to pick your brain with follow-up questions.
The tractor in question is almost exclusively used with a 5' brush mower to keep fields clear around a rural property we own.
In our attempts to get hydraulics working again, we did have a manual that explained the various adjustment screws and I'm sure we had screw D all the way in and out several times and it didn't fix the problem. In your reply, I see something that may be the next thing to investigate. You put emphasis on asking if we had the Traction Booster linkage from the drawbar spring yoke connected. In fact, we do not. It's there but currently hanging down. We were thinking all we wanted the hydraulics to do was raise the mower for transport and so that linkage was not something to worry about right now. It sounds like it needs to be in the loop but nothing in the manual mentioned that or why. I hope you can explain what that does. It would be great if the solution would be that simple.
The property with the tractor on it is about 3 hours away from my home. We will be spending a week there around Memorial Day so I won't have a chance to go hands-on until then but I'll take any advice you have on procedure, order of operations, testing and adjusting (or links to good information on these). Thanks again for your help

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Rotate the Traction Booster lever (on the pump) counter-clockwise enough to allow you to screw in thumbscrew "A" into the pocket/divot made in the pump body to hold the lever so it cannot move. This neutralizes The Traction Booster system, which you don't need anyway. You''ll want screw "D" all the way out, screw "C" all the way out and screw "B" locking the plates together. This will allow you to raise-hold-lower your lift arms.