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Assistance with hitachi EX120-3

Discussion in 'Excavators' started by shelbyk7, Jan 3, 2022.

  1. shelbyk7

    shelbyk7 Well-Known Member

    Joined:
    Jan 3, 2022
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    Location:
    oklahoma
    So tomorrow is going to be 70*F and I plan to test as many things as possible

    How does one go about testing pressures on the pump? Where are the test port locations ? I purchased a kit but cannot find info online at all about where to test
     
  2. mg2361

    mg2361 Senior Member

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    Occupation:
    Equipment Mechanic/Technician
    Location:
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    Did you check the F4 (1A), F7 (1A), F8 (5A) and F9 (5A) fuses

    There is a port just above the output hose of the pump that a gauge can be connected to. You will have to acquire a fitting to put in place of the plug.

    If you hotwired the one farthest from the engine only and it still stalled, then yes it is possible that the solenoid valve assembly could have issues. You could try swapping the whole assemblies to see if that changes anything.

    Unfortunately without being there to hear it (to determine if it is engine power or a hydraulic issue) and without diagnostic equipment so we can clear the codes and see what comes back, we are only shooting in the dark. Try disconnecting the battery for 10 minutes, then connect it and check codes. See if they are gone. I am not sure on those units if a battery disconnect will clear codes. Maybe you could post a short video of the machine and showing how it stalls.
     
    uffex, shopguy and BigWrench55 like this.
  3. shelbyk7

    shelbyk7 Well-Known Member

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    Location:
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    Fuses checked out okay, I will take a video of it stalling and check codes again

     
  4. shelbyk7

    shelbyk7 Well-Known Member

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    Location:
    oklahoma
    Also, can anyone tell me how many of the banjo fuel strainers there are? And where they are located?
     
  5. Tones

    Tones Senior Member

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    Occupation:
    Ex land clearing contractor, part-time retired
    Location:
    Ubique
    There should be a strainer in the outlet of the fuel thank and one in the fuel priming pump inlet.
    2 questions, has your machine sat for a while prior to you buying it?
    Do you have bio blend fuel?
    The reason I ask is I have borrowed a mates tractor and it started doing exactly as you described with your machine. The tractors fuel system was full of snot which I've cleaned out and now is running normally. Diesel here is 4% biofuel and no choice.
     
  6. shelbyk7

    shelbyk7 Well-Known Member

    Joined:
    Jan 3, 2022
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    63
    Location:
    oklahoma
    No strainers, have a rebuild kit for lift pump coming in

    what do most people do about the water separator? My bowl is old and unable to see water or fuel and it’s not cleaning up.

    Am I better to go another direction as far as different separator or should I just get a new bowl (if they sell them)?

    the oem separator is only a separator and not a combination of a filter and separator , right?

    If so, is it beneficial to add an additional filter for fuel system? Something like the racor?
     
  7. shelbyk7

    shelbyk7 Well-Known Member

    Joined:
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    Location:
    oklahoma
    Update

    had some things come up and wasn’t able to work on it much , however the past couple weeks I have been


    List of completed-
    All new hyd fluid, drained cylinders as well best I could (old fluid was very nasty and had tiny bits of rubber from what I believe is the cylinder seals that are leaking)
    -All new filters, fuel, pilot and full flow
    - rebuilt lift pump

    - new seals in swing motor

    -bled the pumps


    started it up first time since I had gotten it and it was running very slow. Like a snail and no power , this surprised me as the last time the issues I had were completely different, normal speed hyd but it would stall under load.

    so I shut it off and gave it some thought and I had forgotten that at some point I switched the solenoids around on the pump, so I switched them back around and boom, back to the way it was acting, maybe a little better now with clean filters and fluid

    my question is this,

    with the drastic change in solenoid swapping, that confirms that one of them is bad, correct?

    move read that the seals go bad and allow fluid to the coil? Can these be re sealed or does it need a new one?
     
    Crushedhitachi likes this.
  8. digger_hunter

    digger_hunter Well-Known Member

    Joined:
    Apr 20, 2012
    Messages:
    135
    Location:
    Germany
    usually what happens with these from what we've come across is the DP sensor/angle sensor or pump solenoid fails. This causes excessive hydraulic oil temp which cooks the seals usually. So if the or rings are solid then it could be what happens. Theres a small control valve with 6 solenoids, make sure you replace the o rings on them as any bypass on those seals will cause a myriad of issues that just don't make sense!. But do check the fuses first to make sure they are all good. I have a manual for this is you want.
     
  9. digger_hunter

    digger_hunter Well-Known Member

    Joined:
    Apr 20, 2012
    Messages:
    135
    Location:
    Germany
    also check the throttle motor cable as sometimes the exhaust muffler leaks and the heat melts inner sleeve of the cable and could be that the cable is sticking etc or not throttling up the engine as needed. just check if it is moving freely especially if the muffler is leaking gas onto the cable.
     
  10. digger_hunter

    digger_hunter Well-Known Member

    Joined:
    Apr 20, 2012
    Messages:
    135
    Location:
    Germany
    usually what happens with these from what we've come across is the DP sensor/angle sensor or pump solenoid fails. This causes excessive hydraulic oil temp which cooks the seals usually. So if the or rings are solid then it could be what happens. Theres a small control valve with 6 solenoids, make sure you replace the o rings on them as any bypass on those seals will cause a myriad of issues that just don't make sense!. But do check the fuses first to make sure they are all good. I have a manual for this is you want.