Another sick Hitachi 120 post

[dirwood]

I am struggling with hydraulic/electrical issues on a Hitachi 120 which seems be fairly common based on my reading here. Problems started out with the operator complaining that occasionally the machine would "stop" mid swing, said it would just slam to a stop while rotating but was never able to see it happen myself as it was an intermittent problem but it did seem to increase in frequency as the machine & weather warmed up. The next issue was that it would only track at a very slow speed, i unplugged the pump control coil and machine was able to track at full speed to allow it to be moved to shop. Seems something is not telling control valve to increase pump stroke, and i am not sure where to start? Angle indicator, pressure sensor, ??. Also curious if the swing issue could be caused by a pump going to minimum stroke and the pressure dropping so quick it is setting swing brake. Located in a pretty remote area and getting any outside help means boat and or plane rides so we would really like to get this problem resolved ourselves if possible. Thanks for any information or tips you may be able to provide.

 

[knightgang]

Mine is acting up as well. I thought mine was a fuel delivery issue and I am still not convinced that it is not a fuel issue.
I have a EX120-2, a couple of weeks ago, I found that one issue that I was having appeared to be that the fuel shut off cable was partially pulled restricting fuel flow. After releasing tension on it and cranking it up, after a few minutes to the idle smoothed out and I I used it all day with no issues, used the bucket to mix and dump concrete and stacked a large pile of stumps for burning. The next use, it started bogging down again anytime you touch the hydraulics. Once this starts, even without touching the hydraulics, it sounds as if the engine is struggling to run. Usually, if you shut it down for a few minutes, then once it refires and you hit the idle button and then run through the throttle settings, it might smooth out, sometimes it might not. But once this issue starts, you can't track the machine or hardy touch the hydraulics with out the machine shutting off.

I keep wondering if it is because of something electronic sending the pump into full wash and bogging down the engine or if there is something else causing a fuel restriction issue. I see smoke form the exhaust once in a while, but honestly, I don't see smoke when it is struggling to run and I can't recall seeing smoke when it is this state and I hit the hydraulics. I need to get this sorted out quickly and we are soon to need this machine for final cleanup at my homebuild site and once we get moved in I have a lot of earth work to do from ditch maintenance to pond digging, etc. You get the idea.

 

[dirwood]

while testing the swash angle sensor, i noticed every time i moved the harness around i could hear the pump displacement changing, kept poking around and found the rpm sensor on the pump had a broken wire and was making/breaking contact while i was wiggling the harness around. Repaired the wire and hopefully that will fix the issues, hard to say for a while as the problems were intermittent most of the time.