I have a lawnmower with a hydraulic problem that I cant diagnose. I'm not sure if it's the pump, wheel motor, or dump valve. Can anyone give me some advice on how to find out which is the problem? Both wheels stopped driving at about the same time and they each have their own pump and wheel motor. Right now one wheel moves slightly and the other does absolutely nothing. I'm not super knowledgeable about hydraulics, but I think I can fix it if I can diagnose which part is the problem.