I responded with this on another thread, but then thought better of piggy backing someone else's thread. Figured I needed to post a new thread and there may very well be two separate issues with these machines. My EX120 is acting up. 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.
First thing to check if the little plastic strainer inside the banjo fitting on the inlet side of the fuel filter housing if you haven't already.
Sometimes they move them around too, I usually start wherever the fuel line from the tank connects and work my way all the way to the injection pump, check all the hollow bolts. One machine I found three strainers, never did figure that one out. Only the first one was plugged of course.
What colour is the smoke? To me it sounds like your pumps aren't destroking causing your engine to labour. If it's black smoke then you're most likely not having fuel issues, rather the engine is working overtime to try to overcome the pressure the pumps are causing by not destroking. As far as I understand it, Your hydraulic system is a closed center system with electronic pressure regulation, and when the regulation fails the pumps go to full stroke and the fluid has nowhere to go except over the relief valve, then when you move a control it blocks the flow off completely and the engine can't overcome the additional pressure and therefore stalls. What I recommend is to check all your wiring very carefully, on my 200-2 the wiring looked ok after I fixed some of the obvious problems but ended up being bad all over the place so I just replaced the whole mess and haven't had a problem since. Intermittent wiring problems can be a bugger to diagnose because of their intermittent nature, they tend to hide when you're looking for them as often you move the wiring trying to gain access and now you've moved a wire just enough for it to have continuity again and it test out fine, only to act up again when it gets to that certain spot... That is what was going on with my machine at least. You can also put your machine in limp mode to be able to move it and do limited work with it if you need it before you get a chance to fix it properly, but it will be Slooooow. To do this you'll need an 8mm (don't quote me on that, just going by memory here but it's been 6 years since I dis this) allen key. Go back to your pumps, on the bottom you will find a rectangular plate held on with 4 Allen bolts. On my machine it's located where I'm pointing in the picture, your machine might be slightly different, I've never actually seen a 120 up close so this may not even be the way you do it on a 120 but someone will let us know if I'm wrong... Pull these allen bolts out and then pull the plate straight down. You may need to pry on the plate with something but it should come out fairly easily. Once you have it out you'll see a rod sticking up from this plate. Turn the plate and rod assembly 180 degrees and shove it back in the pumps. You'll feel some resistance as you push it in, this is pushing the piston that controls the pump stroke up, destroking your pumps. If you can't push it up, loosen off the small pilot line at the top of the pump to release the pressure in there. It will puke out oil when you push up on the piston, sombe ready. On e the rod and bolt assembly are back in put the allen head bolts back in and you're now in limp mode. Don't forget to do up the pilot line again if you had to undo it. Hope this helps!