4430 Power Beyond Return Pressure
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    4430 Power Beyond Return Pressure

    I've been helping my neighbor install a joystick control on his 4430 for the front end loader. We are running the loader valve off of a power beyond block. We got it all hooked up and when you push the joystick into float the loader raises. I have determined the return pressure is too high for the valve to allow the loader to fall in the float position. The return pressure is between 400 and 500 psi depending on engine speed. Is there anyway to check for a restriction in the charge pressure circuit? Or have I done something wrong. Thanks in advance for the help.

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    Welcome to GTT
    Did you install PBY block on LH side of rockshaft housing? Do you have in port of JS valve attached to top port fitting(key 6)? Does scv that's attached to PBY operate correctly?
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    Yes PBY is on left side. What do you mean by JS valve? As far as I know SCV is working correctly. We had the PBY on the right side first then moved it to the left. Same problem.

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    JS=joy stick

    You could consider routing JS valve return oil to sump.
    Last edited by Tx Jim; 04-04-2018 at 08:24 AM.

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    We tried that and it cause the main hydraulic pump to chatter violently. He just told me when he bailed hay with it last year the baler hydraulics ran real slow. Now I’m wonder about the SCV. What exactly could be wrong with those that would cause it to do what it is doing with the loader?

    Thanks again.

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    With JS lever in neutral disconnect return from tractor then aim hose in bucket,start engine does any hyd oil exit open JS return hose? To check scv get a 5000# gauge then plug gauge into each side of breakaway coupler then activate lever each direction,once lever is returned to neutral pressure gauge should remain at constant pressure(stand-by pressure) unless scv poppet valves are leaking. Routing return oil to sump should have little affect on frt hyd pump. Way back when I had a loader on my 4255 I had JS valve on FEL return routed to sump with no adverse affect on hyd's.

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    I will try the gauge in the SCV ports. Yes we are getting return fluid from the JS valve. When we tried sticking the return hose in the filler neck. The pump cavitated so bad the whole tractor shook. Thanks again for the help.

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    No oil should exit open JS valve return hose when engine is running when JS is in neutral. Does JS valve have a closed-center plug with seal installed???? Check your personal messages because I sent you one.
    Last edited by Tx Jim; 04-04-2018 at 12:23 PM.

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    I found out today that the valve is open center. Also I did not realize that John Deere is a closed center system. We have a closed center plug order for the valve. I think we have this thing figured out. Thanks again for the information.

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    Thanks for update. Open center valve utilized on a closed center system will cause frt pump to cavitate as you have discovered. I still remember the 1st time I encountered a blown seal on a closed center conversion plug way in the late 70's. The tractor I was diagnosing for poor hyd's was a JD 2020 with a 48 frt loader.
    Jim
    Last edited by Tx Jim; 04-05-2018 at 05:41 AM.

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