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Hitachi Ex120 Problem

Discussion in 'Excavators' started by spunkeymonkey, Jul 7, 2009.

  1. spunkeymonkey

    spunkeymonkey New Member

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    I have a Hitachi EX120-1. It started stalling when the hydraulic pump was under load. At the same time, the engine started to run hot, and the hydraulics became really fast. Various people have looked at it, one said the pump was u/s, so I took it off and took it to a pump specialist, who couldnt find anything at all wrong with it! I believe it is an hydraulic problem, rather than a fuel problem, because the engine recovers its revs straight away when you release the lever. At some time in its former life, a lot of wires to the pump had been cut, and rejoined by twisting together, the machine worked for many years like this. I have remade all the connections, and it has slightly improved how the machine works, you can at least dig now, although the engine still stalls when a ram goes to its full extension or retraction, as though the pump is at full swash. Has any one else experienced anything like this? All suggestions gratefully recieved!
     
  2. Wardiker

    Wardiker New Member

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    I had a very similar problem but with my EX60 URG unit. It was a clogged fuel line. Check my posts, might be some good info for ya there from the people that helped me and saved my a lot of time and money.
     
  3. 482budget

    482budget New Member

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    I got a 120-3 and when the fuel filter plugs it with in hours when you notice it till when she won't even move. Make sure you chwck the pre filter that is screwed in to the bango housing before or on the spin on filter housing.
    The only other thing I could think of would be the rpm sensor not working but can't see that.
    I went though this once and I wound up cleaning eveything from the tank back.
     
  4. willie59

    willie59 Super Moderator

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    That little tidbit of info leads me to think it's not a fuel problem. If an engine is slowing/stalling under load from a fuel restriction, when you release the load, the revs will slowly recover. If the revs recover rapidly when load is released, fuel is flowing freely. ;)

    I've worked on dash 2's, no dash 1 machines. I'm almost certain they have different pumps. It does sound like you have a pump overstroke problem. Do you maybe have a problem with the swash plate angle sensor? Or do your pumps even have one? I don't know how to test them. But I did have a dash 2 with a faulty plate sensor that caused the same symptoms you describe. I removed the plate sensor from another working dash 2, installed it on the problem machine, it was then healed. :D
     
  5. krich

    krich New Member

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    Whats the serial number on your machine, also when the engine stalls does the engine black smoke or is the exhaust clear/ no smoke
     
  6. spunkeymonkey

    spunkeymonkey New Member

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    I made a mistake, it is an EX120-2! There is black smoke from the exhaust as the engine dies, this clears when the revs recover. Where is the swash plate angle sensor located?
     
  7. willie59

    willie59 Super Moderator

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    When you open the right rear door, your staring at the rear of the hyd pump. On the right side of the pump is a round thing with, I think, two wires going to it. That's the angle sensor. You could remove it to check the tab that turns the sensor and the coupler that it seats into, but before you remove it, mark the position of the sensor. It's position is adjustable by loosening the allen head mounting screw and rotating the sensor via screw slot, this is for fine tuning of the angle sensor operation. Like I said, I don't know how to test the sensor, I was lucky and had another working dash 2 right next to it. With your engine loading and blowing black smoke, it does sound like your pump is overstroking. Hope ya find your problem. ;)
     
  8. spunkeymonkey

    spunkeymonkey New Member

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    I finally found a sensor to try on my machine, but it made no difference! Also now, the machine will not rev up, none of the power setting buttons work.
     
  9. -3Doc

    -3Doc New Member

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    Sounds like the N sensor is not working, Check wiring to sensor on top of pump also known as the rpm sensor. Looks like a button held in with one bolt.
     
  10. spunkeymonkey

    spunkeymonkey New Member

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    Ive had time to have a mess with the digger today! I have got the buttons to work to rev it up, it was a bad connection in the cab. The machine is slightly better than it was, but it still stalls. It is as though everything is running too fast, and the engine cant keep up. There is a tortoise-hare button, but nothing seems to happen if you press it. The leds work though. Is this just for the tracking, or all the hydraulics? Could it be a bad wire somewhere making everything too fast? Also, when I had the pump off in the beginning, the coupling between the pump and the engine was all chewed up. Could this cause any symptoms? Thanks in advance for any help!
     
  11. -3Doc

    -3Doc New Member

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    Tortoise Hare button is only for travel speed, check for more wiring issues in cab for other problems as well, it sounds like your pump is going to full swash and staying there. This is an indication that the pump displacement solenoids are not working properly, check all fuses and make sure they are the proper rating, two of those fuses are for pump displacement solenoids. Also check that the wiring to the solenoids is good and also the wireing to the angle sensor is good. Has anyone been messing with the angle sensor? Looks like a small top hat on the right side of the pump.
     
  12. -3Doc

    -3Doc New Member

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    If you had the angle sensor out you may have put it back in in the wrong orientation, there is a small dot on the shaft and when you put it back in the dot must face away from the harness side. You then must set the sensor to the proper voltage, I can explain that later as it is a bit complicated, make sure the orientation is correct first then try it and see if it is somewhat better.
     
  13. spunkeymonkey

    spunkeymonkey New Member

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    Ive checked all the wiring, and checked that the dot on the shaft is facing away from the wiring. Now you can explain about setting the voltage on the sensor!
     
  14. -3Doc

    -3Doc New Member

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    I have sent you an email with the page from the manual to set the voltage. Let me know how it works.:)
     
  15. spunkeymonkey

    spunkeymonkey New Member

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    You, Sir, are a true gentleman! Thank you very much. I shall try that tomorrow morning. Were these dash 2 excavators supplied new in Canada?
     
  16. -3Doc

    -3Doc New Member

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    Yes and also many gry market machines were imported.;)
     
  17. spunkeymonkey

    spunkeymonkey New Member

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    I have carried out the procedure you emailed me. The machine is no different! Any other ideas?
     
  18. -3Doc

    -3Doc New Member

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    :canada Take out the angle sensor and put a flat blade screwdriver into the slot were the angle sensor goes and try to easily turn the shaft that is in there. It should only turn very little if it turns easy then let me know. You should not be able to turn it more than about the width of a hair.:)
     
  19. -3Doc

    -3Doc New Member

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    :)Is the machine good when you first start it and within 3 minuets it is smoking and stalling under load?
     
  20. spunkeymonkey

    spunkeymonkey New Member

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    I havent tried putting a screwdriver into the sensor slot yet, will do tomorrow morning. The machine smokes and stalls from cold.
     

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