1. Thank you for visiting HeavyEquipmentForums.com! Our objective is to provide industry professionals a place to gather to exchange questions, answers and ideas. We welcome you to register using the "Register" icon at the top of the page. We'd appreciate any help you can offer in spreading the word of our new site. The more members that join, the bigger resource for all to enjoy. Thank you!
  2. ALL NEW MEMBERS READ THIS FIRST!! Thank you for joining Heavy Equipment Forums! If you are new to forums we communicate with "Threads", please search our threads to see if your topic may have already been answered and if not then click "Post New Thread" in the appropriate forum. This will allow all of our members to see your question and give you the best chance to be answered. After you've made a number of posts you will graduate to Full Member status where you'll see a few more privileges. Following these guidelines will help make this the best resource for heavy equipment on the net. Thanks for joining us and I hope you enjoy your stay!!

Hitachi Ex120 Problem

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

  1. igor

    igor New Member

    Joined:
    Jan 26, 2010
    Messages:
    3
    Location:
    Australia
    I have been helping the father-in-law with his EX120-2 (serial 12N-35444)as we have some real issues with. the machine would run untill it was hot and then any work on the hydraulics would be like this one in this tread, lots of black smoke with the hydraulics loading it up something shocking. We have had issues with the Hydraulic computer dying as well as the odd fuse blowing. To cut the story short, the computer had a resistor burned out (R1, 10 ohm 4W) This was replaced and all the push button modes came back to life and I think we had to replace Fuse 6, Sw.Box. All seemed ok, but when we had a big job and the maching had to work hard for 30-45 minutes, then the fault returned.
    I had monitored the heat on the resistor when we started and it was ok, but it had failed again. We have since put another resistor in and I cant seem to find anything else faulty on the computer (I am an electronic tech by trade) and done a search of the whole machine for wire shorts etc and did finally find one on the wires to the quick hitch solenoid, the insulation had rubbed through and may have been randomly shorting the 24V outs. That may explain the fuse failures. We then (after reading the posts here) measured all the coil (solenoids) resistances, all (SA, SB etc)were around 23 ohms on the digital meter, however SI measured 60 ohms, (I dont have the manual to show what each one controls, but the wiring loom was labeled) but this is a slightly different device in appearence, is this normal? It seemed stable, so I concluded that it may be ok and felt that since the computer pulled to ground to turn it on, it would be unlikely to cook the resistor in the computer which is on the 24V rail.... Again to cut the story short, we restarted digging and were working it hard for some time, a trench in mud rock 8' deep 40' long 4' wide before the hydraulics stopped again, with the computer down with R1 overheated....
    Without a detailed circuit diagram, I'm a little lost for ideas now....
    Has anyone had issues with the computer blowing after working the machine to it gets hot? We were quoted around $3K for another computer, so it isnt a easy thing to replace when it's likely to blow from something external to it.
    Suggestions anyone? Are circuits available anywhere?
     
  2. -3Doc

    -3Doc Well-Known Member

    Joined:
    Jul 29, 2009
    Messages:
    119
    Occupation:
    Ticketed HD Mechanic
    Location:
    British Columbia
    :canada Send me a PM with your email address and I will send you the schematics.
     
  3. igor

    igor New Member

    Joined:
    Jan 26, 2010
    Messages:
    3
    Location:
    Australia
    Hi 3Doc, thanks for the kind offer, I am a newbie here, so dont seem to have permissions to email you.... or I just cant seem to find you info without getting a permission problem. However, my email is igor@rmit.edu.au
    I hope that doesnt violate the rules here....
     
  4. fenton

    fenton New Member

    Joined:
    Jan 28, 2010
    Messages:
    1
    Location:
    Ireland
    Hi 3Doc, I'm looking for the manual for an EX120-2 also. If you could PM the manual, I'd be very greatful. Thanks.
     
  5. duck_nutt

    duck_nutt Member

    Joined:
    Jan 20, 2010
    Messages:
    16
    Location:
    mississippi, usa
    me too plz
     
  6. duck_nutt

    duck_nutt Member

    Joined:
    Jan 20, 2010
    Messages:
    16
    Location:
    mississippi, usa
    I can't start my on thread yet, so I'll ask here.....paw-in-law says the swing manifold has a small leak....it that just an O-ring?
     
  7. ATP

    ATP New Member

    Joined:
    Feb 1, 2010
    Messages:
    2
    Location:
    Georgia
    490e

    We have replaced the pump drive in a 490E and are now having trouble with the up boom function. No solenoids or sensors were removed from pump and all wires were carefully marked and replaced. All other functions work correctly. At idle it lifts fine but as soon as engine revs boom slows. It also suddenly worked great for about an hour then started messing up again. Boom down works great only booming up is giving problems. Any ideas?
     
  8. bigkit

    bigkit Member

    Joined:
    Sep 10, 2009
    Messages:
    19
    Location:
    Sussex, England
    Just a thought, I have had a few hitachi /3 and /5's and some have a banjo fuel filter in the fuel line as it enters the pump. (A bitch to get at!) Maybe something of use on another day.
     
  9. bigkit

    bigkit Member

    Joined:
    Sep 10, 2009
    Messages:
    19
    Location:
    Sussex, England
    Oh, and I've got Hitachi manuels for EX120 /3 and/5 excavators if anyone needs page.
     
  10. -3Doc

    -3Doc Well-Known Member

    Joined:
    Jul 29, 2009
    Messages:
    119
    Occupation:
    Ticketed HD Mechanic
    Location:
    British Columbia
    If the manifold is leaking out the top then it is time for a reseal. The manifold must be removed and pushed apart and all seals and orings replaced. Not a huge job but you must use a press to push it back together.:canada
     
  11. ATP

    ATP New Member

    Joined:
    Feb 1, 2010
    Messages:
    2
    Location:
    Georgia
    Thanks for the fuel line info. I will remember this.
     
  12. 1st AD

    1st AD New Member

    Joined:
    Feb 10, 2010
    Messages:
    2
    Location:
    Texas
    Deere / Hitachi Pump controler

    Does anyone know the specs on the diode in the pump controler on the power inlet pin number 37 on the connector ?
     
  13. duck_nutt

    duck_nutt Member

    Joined:
    Jan 20, 2010
    Messages:
    16
    Location:
    mississippi, usa
    thanks -3Doc....i'm an air traffic controller, but the longer I stay around my father in law, I'm turning into a mechanic....helped him put on new seals on the 2 boom cylinders and the 1 arm cylinder....those things are kinda heavy!
     
  14. igor

    igor New Member

    Joined:
    Jan 26, 2010
    Messages:
    3
    Location:
    Australia
    Help on EX120-2 PVC computer

    If you are talking about the PVC computer for the Hitachi EX120-2, I have one on my desk right now I'm trying to fix.... The diode, labeled D1 is in series with a 4W 10 ohm resistor, on the Father-in-laws machine, which I have to fix the resistor was blown open and the diode went short circuit, so I have had a massive overload there to do that. The diode has no markings, but if you consider the power rating of the resistor, then the max current would only be around 0.6A( for max power rating on the resistor), but it seems to pull only 0.15 to 0.22 A on normal operation, so just about any generic diode probably would work. I used another glass passivated diode rated at about 1.5A that is just a fraction larger than the original, but any 1A diode should work. If you have a simular issue to me, then I'd be interested in what else you find. My email is a few posts back. I replaced the resistor then it all worked fine in the machine for over half an hour of hard work, then suddenly blew again. I'm an electronic tech but I cant reproduce the fault. However, the computer is still faulty. (tried in another machine)
    Does anyone have the schematics for these computers? Or a cheap second hand computer!
     
  15. TraxterMaster

    TraxterMaster Member

    Joined:
    Mar 10, 2010
    Messages:
    13
    Occupation:
    Farmer
    Location:
    Ottawa, Canada
    I have the exact same issues with my EX100, I dont know wich generation it is but i think its a gen 2. I can tell its a 1994 and it has the round corner cab and a 4cyl non-turbo with a mechanical fuel injection pump control over cables to electric motor. fuel filter is new and blown all the lines to make sure they are clean and its still bugging/stalling when any hydrolics fuction are activated. it does it from dead cold to hot. It might be selenoids or sensor on the pump.

    3-Doc do you have the repair manual for the EX100-2
     
  16. XxTrasHxX

    XxTrasHxX Member

    Joined:
    Jan 27, 2010
    Messages:
    20
    Location:
    Toronto Canada
    Have you guys looked at the air inlet hose that goes from the air filter housing to the turbo,
    they get soft and will collapse when there warm and under load. Causing black smoke and stalling , this is a common problem on older Hitachi and John Deere machines, just have some one stand up top while unit is under load to see if it collapses.

    Hope this helps
     
  17. newbe

    newbe New Member

    Joined:
    Mar 11, 2010
    Messages:
    1
    Location:
    Ireland
    EX 120-2 Manuals

    Hi -3DOC,
    New member here, was browsing through this forum as i too had the same problem with my EX120-2 going back some weeks ago and after alot of trouble shooting i found that one of the pump solenoid valves was defect and since i changed it my machine is working perfect, Basically i was wondering if you tell me where i can get my hands on Tech manuals, wiring diagrams and illistrated parts catalog for this machine as it never came with any. I have searched through the internet a few times and still can't come up with anything. I would be most gratefull if you could help me out on this, thanks
     
  18. TraxterMaster

    TraxterMaster Member

    Joined:
    Mar 10, 2010
    Messages:
    13
    Occupation:
    Farmer
    Location:
    Ottawa, Canada
    I went working on our EX100 and starting with the fuel system changed the filter and verified for the banjo fitting and the mesh was missing. it had a 15amp fuse blow, I beleive it was the 3rd one in the second row of fuse the fuse door is missing so i dont know whats it was use for. I tried to swap the connection on the selenoid and didn't do anything different. I recalibrated the angle sensor to 4.40V on the dot after running the engine idle for 4 min with selenoid unplug. It improuved a little after but its not working perfectly.

    What is the normal resistance in the selenoid valve. The engine sounds like its under constant load.
     
  19. -3Doc

    -3Doc Well-Known Member

    Joined:
    Jul 29, 2009
    Messages:
    119
    Occupation:
    Ticketed HD Mechanic
    Location:
    British Columbia
    Is the engine under load as soon as you start it or only after you put the safety lever down?:canada
     
  20. TraxterMaster

    TraxterMaster Member

    Joined:
    Mar 10, 2010
    Messages:
    13
    Occupation:
    Farmer
    Location:
    Ottawa, Canada
    Well it resonates in the cab at idle more then it use to. the lever up or down doesn't change the sound of the engine. also forgot to mention the connection at the RPM sensor on the pump was broke, I replaced the connection still does not work properly. If crawl slowly but steady on flat ground you can hear the engine trying to keep up but still bugs down to a stall if i push too much. I was barly able to put it back on the trailer to bring it home yesterday. The engne load is pretty high because you could see the heat mirrage over the engine cover after I stoped it. Theres alot of wires in this machine that need to be looked at but a wiring diagram could be useful. my temp gauge doesn't work and alternater light is on but it charges. :canada me too