Tech Tips - What is Charge Pressure 

Your type of machine has an open loop closed center hydraulic system. Nothing in this video applies to your system. The problem you describe will be in one of three places. 1. The load sense circuit is not calling for pressure. 2. The system relief is defective. This would cause your hydraulics to get hotter than normal when under extended load. 3. The new pump is defective. If I was working on your machine. I would install the hydraulics and use a temperature sensor to check if the inlet end of the control valve is getting hot over a couple minute time frame. That is based on my assumption that the system pressure control valve is located in the inlet section of the hydraulic valve. If they didn't find a problem there, depending on my resources, I would have to choose if I send the pump out for testing or test the system to find out if the load sensing is working. If I wanted to check the load fencing myself I would look at the pump control for the small test part probably number four size. it will be a couple hundred pound to lower than system pressure. If that difference stays the same when it's under load the pump is making the pressure it is asked to make. If the difference decreases before the system reaches operating pressure, the pump has a problem Good luck

Somewhere on the charge circuit, often on the charge filter, sometimes in a fitting. The exact location depends on your specific machine.