I'm looking into a beat up Hitachi EX200 that has a number of issues, but one in particular I'm hoping for some insight on - according to the dealer selling it it has a hydraulic pump issue. It will run and dig, but apparently the pump bogs down under load, and will come back to normal when you let off the sticks. According to him / his mechanic, they believe it's an electrical issue - something related to a valve triggering or the pump not stroking automatically. That's the sum of the description I have so far, and I haven't been down to look the machine over yet, which I'm likely to do with an inspector soon. Not a ton of information to go on, but I'm hoping the description of the problem that I have so far is enough to point to likely potential causes. Basically looking for where on the gamut this is likely to fall from 'clogged filter somewhere that the dealer doesn't want to deal with on a cheap flip' to 'computer or pump likely shot, don't touch'.
Good day JR The majority of excavators today have pump regulation controlled by two elements - pressure - & engine power, the pressure is straight forward at high pressure the pump will de-stroke reducing the output. Power control comes in different methods -mechanical - electric - electronic what is often a mistake is that something hydraulic causing the issue in fact the answer is much simpler loss of engine power. Recommend you begin with the motor. Kind regards Uffex