I have a Euromach 6500 walking excavator with a Kubota F2503-TE engine. The engine runs great, idle to full throttle. However, when I put a load on any hydraulic function, it will bog the engine down. When the load is removed, the engine will rev up high for a second, then return to the set speed. The engine seems to be getting plenty of fuel evidenced by the black smoke. I believe it is probably a problem with a check valve, but not sure. Any ideas for where the problem might be would be appreciated. The youtube link below shows how it acts. Thought maybe somebody might have had this type of problem before. Thanks. http://www.youtube.com/watch?v=_-AleEy2-J4
Not very familiarized with this type of equipment, if it has a piston pump you should check for the Pressure compensation solenoid.
Try your fuel filters. I've had exactly the same issue on my cat 303. 2x in the past 150hrs or so. idles good, starts good, as soon as you load up the hydraulics, she shakes and bogs down. As soon as let go of the sticks, all is well again.....
Has anyone fiddled with the governor
Thanks for everyone's suggestions. The filter and lines have been changed. We thought it was a weak fuel pump, so we changed that. None of this made any difference. Since the first post, we cranked it up one morning and it started running rough. Figured out we had a stuck injector pump. Turns out it was a broken spring and is being repaired. Hope to put it back on today and try again. To my knowledge no one has messed with the governor. I will check into that further.