I have to look at a JCB JS330 next week that has a hydraulic issue. After having the hydraulic pump rebuilt the engine now pulls down and stalls when using any function. I'm looking for the adjustment procedure to check and reset the pump regulators. It a Rexroth pump and a 9050B Case or a 4300Q LinkBelt is the same machine. I have all the 9000B series Case manuals except this one.Don't know for sure that this is the problem but I think it's a good place to start.
I drove a JS330 for about a year and it gave a lot of trouble with the hydraulics. I saw the Irish JCB distributor's fitter check and adjust the pump. I am not able to tell you what to do, but the switches on the pump are prone to be faulty, just something to be aware of. I don't think the fitter ever got to the bottom of the problem. A guy working beside me on a Komatsu 340 could fill a Volvo A40 dump truck in the same time it took me to fill an A25, with identical buckets. Hope you figure it out...