Mitsubishi: I am putting a hydraulic thumb on my excavator heads

Posted on Feb 5, 2014

The excavator is Mitsubishi MS280. The problem is they are not sure how to excite the pump, I want to put an electronic proportional control valve in the old girl. If your familiar with this era of Mitsubishi`s could you let me know and I will give you as much detail as I can. I will try to explain what I have and what I believe is happening. The

Mitsubishi: I am putting a hydraulic thumb on my excavator heads
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levers are mechanical linkage to what I think is pilot valves under the cabin. The other side of these valves is also mechanical linkage to the control valves. The reason I think they are pilot valves is because there is a separate gear pump on each of the main pumps. These gear pumps are plumbed to these valves and to tank. So what we did was disconnect the mechanical linkage between the pilot valve and the main valve and installed a gauge on the main pump which we expected to see pressure when we activate the corresponding lever to the pilot valve, but the pump did not excite and we had no pressure. So whilst the linkage was disconnected from the control valve we moved the spool in the valve and that excited the pump, so maybe there is some internal porting in the control valves. If so why would there be what look like pilot valves, I can`t understand there purpose with this test we did. I did try to add a diagram of the hydraulic circuit from the doggie manual that I have, they call the pilot valves, servo valves, but I was unable to get a clear picture to attach to this message, I tried for an hour but the resolution is so large it was unviewable, I don`t know why as on my computer it read fine, I even put it on PDF and it came up well, but couldn`t attach it to here. If you have any other way I could send it to you please let me no. Yeah, ok. I haven`t progressed any further here with anybody. Like I said though I do...

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