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Thread: Anyone a hydraulic genius

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    4 Star General dmetalmiki's Avatar
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    AS mentioned previously, Check the routing of the pipes.
    Also, There are relief valves in the circuit, Check if they need servicing, As they may be 'blowing off' prematurely.
    And I just had a thought...Check the selector levers as they may well not be functioning properly.
    If a selector is not closing properly that would cause immediate loss of pressure, And could? let the oil bypass to where it should not. > Hence the two operations' working simultaneously<,
    And perhaps? is the cause of the failure to lift properly.
    If you can, And if possible, Have someone to check all pressures at the operating points.
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    4 Star General frank8003's Avatar
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    Quote Originally Posted by wheelspinner View Post
    Attachment 778443

    Ken, I have the entire air, electrical and hydraulics schematics combined into a single file. I'm going to try and upload them

    Edit: The whole file was 33 M and too big to upload, so I culled it down to just the two pages on the Wrecker Hydraulics
    One can send really large files for free with google. It is called google drive. You and the reciepiant must have google but that is only limitation I have seen.
    I have google so just send the entire 33mb to frank800man@gmail.com as a mail attachment.
    These files should be in SS database.
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    4 Star General Coffey1's Avatar
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    20191005_144726.jpg

    Got it to pick up rear but won't pick front up.
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    Are the control valves rotary(valve core rotates) or push/pull(core slides in or out) spool type? Push pull spool type usually have o-rings at the ends and close tolerances inside, so they always work, but can leak at the ends.

    Rotary type often have o-rings dividing the halves of the valves so can leak across from one circuit to the other.

    Don't have a drawing but it sounds like you might have a leaking relief valve. But what could also be happening is you are loosing pressure from one side across to the other thru that selector valve as soon as you load up the system. The both circuits working regardless of selector position description is another clue. That or it was disassembled/de-installed in the past and not reconnected/re-assembled correctly...

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    4 Star General Coffey1's Avatar
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    20191005_081922.jpg

    The winches are bad to the bone, pulled these big rocks from behind my house. Monday I'll load them up with crane and put them somewhere useful.
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    The lines would have to be crossed somewhere upstream because there's absolutely no way to get them wrong at selector valves.
    They are large hard lines.
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    4 Star General Floridianson's Avatar
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    How bout internal leakeage in the ram it's self?
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    Yea, could also be a bad ram seal, but the selector not cleanly separating the two operations I think may be a big clue...

    Duh, I have had a similar issue on a different type system. Have you tried loading up both systems simultaneously? IE: Try and lift the front of the LMTV that you cannot get off the ground, and while doing that try and operate a crane function that is already maxed out, like boom down when the boom is already against its down stop. Powering to an end stop usually causes pressure to build to maximum and open the relief valve.

    Pressure = force like to lift the truck, Flow rate = the speed at which it happens. If fluid is escaping from the wrecker side thru a bad control valve seal into the crane side when you put the wrecker under load, it cannot build enough pressure to perform the work/lift to full capacity.

    If while trying to lift the truck with the wrecker, you simultaneously try to build pressure on the crane side where fluid is escaping to, the wrecker side will also build pressure as the escape path is now blocked/restricted. If the wrecker lifts when you do this, the selector valve is most definitely leaking past...
    Last edited by Ronmar; 10-05-2019 at 21:35.

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