Those three going to the loader valve are these three on the manifold. Bottom left goes to middle on loader valve pic. Top left going to far right on valve pic. Right on manifold goes to far left on valve.
I did not realize how different the LB series was from the LK. I was hoping to see a pump similar to the ones on the LK models. That one mounts upside down from the LK.
I can not tell from the loader valve picture which is which. Usually they are stamped somewhere by each port. P=power in, T=tank and C=power beyond. Most likely on the bottom of your valve.
You are correct to locate the power beyond and check flow rate there. That will be after the diverter valve. The diverter also is splitting what flow you have for the power steering leaving very little for the loader and 3pt. This will probably be less than 1GPM at this point.
I would check on what pumps are available. Unfortunately the parts lookup does not show your model so I can not help with that. You may just need to call Michigan Iron and talk to them about pump options.
I was able to get fluid out of the hose I disconnected, it was going much slower than my previous flow test so I didn’t bother measuring and also I wasn’t able to pin point which position my diverter should be in. So my first course of action should be to source a new hydraulic pump to put on the tractor? Also is the function of the power beyond just to get rid of fluid while the loader valve is idle?
Power beyond allows adding additional valves to the system. The loader valve feeds your 3pt hitch valve through the power beyond port.
I hate to say it but yes I am thinking a new or rebuilt pump is needed. You should see if a local hydraulic shop can rebuild yours. You still will have to sort out the priority/diverter valve as well.
I would look to see if they every offered a higher flow pump for your model. I was able to go from 7GPM pump to a 10GPM pump on my Kioti. But I knew the condition of the rest of the tractor and was comfortable it was worth the price of the new pump.
If you are getting air the small Rubber hose feeding the pump is a common issue. The O-rings at the fittings can also allow air into the system.
Sometimes you can find the leaks by coating the connection points with grease. This is done one at a time then test to see if air is eliminated. If not coat the next one.
I do not know of any other replacements for the priority/diverter valve.
Another question I have is about the 3pt control. Some of these did not have position control valve. With position control the 3pt moves with the movement of the lever and you can leave the lever at any position you want.
The other type you raise the lever all the way up till you reach the desired height then return the lever to center. To lower you move the lever all the way down to desired height then return to center. Do you know which type you have?