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!!

1999 JLG 450A with a drive problem

Discussion in 'Forklifts/Telehandlers' started by davis1676, Sep 28, 2012.

  1. davis1676

    davis1676 Well-Known Member

    Joined:
    Sep 28, 2012
    Messages:
    53
    Occupation:
    facilities supervisor
    Location:
    Hooks, Texas
    I have been back on the drive pump problem with this thing. Since I posted last I have taken pump off machine, tore down the pump and looked over and cleaned and inspected every piece of it. I did not see anything that looked of concern or damaged in there. I replaced all the gaskets and o rings and put the pump back on the machine. I have charge pressure at idle around 900 psi. Really dont know where to check for the high pressure side. Anyone worked on this kind of pump can tell me where to check High pressure. I am not sure the EDC is working proper but there should be a way of checking the pressure so I can at least eliminate the pump itself not working and then put my attention to the controller.

    low pixel drive pump 5.jpg
     
  2. VoodooMojo

    VoodooMojo Senior Member

    Joined:
    Jan 18, 2012
    Messages:
    344
    Occupation:
    Sr Technical Service Representative
    Location:
    Baltimore, East Coast USA
    ouch!
    900 psi for charge pressure is way too much, sounds like the null needs adjustment.
    If the null is adjusted properly then try removing a shim or two from the charge relief valve.
    400 psi is the correct setting.
    The swashplate may be stroked beyond neutral. This could be caused by the servo piston on the pump not being centered or the EDC not being centered.
     
    Last edited: Oct 20, 2012
  3. davis1676

    davis1676 Well-Known Member

    Joined:
    Sep 28, 2012
    Messages:
    53
    Occupation:
    facilities supervisor
    Location:
    Hooks, Texas
    how much pressure should I see on the servo test ports. I hooked up a gauge to both sides and tried to move the adjustment screw ( cant see it in the picture, its on the backside) and didnt get a reading on either side. I thought the charge pressure was up there, I seen about five shims behind the spring on the charge relief valve. Will that high charge pressure interfere with servo piston moving back and forth?
     
  4. davis1676

    davis1676 Well-Known Member

    Joined:
    Sep 28, 2012
    Messages:
    53
    Occupation:
    facilities supervisor
    Location:
    Hooks, Texas
    how much pressure should I see on the servo test ports. I hooked up a gauge to both sides and tried to move the adjustment screw ( cant see it in the picture, its on the backside) and didnt get a reading on either side. I thought the charge pressure was up there, I seen about five shims behind the spring on the charge relief valve. Will that high charge pressure interfere with servo piston moving back and forth? There is such a small movement on the EDC to create a forward and reverse on this pump. Thanks for the reply I will try what you said.
     
  5. VoodooMojo

    VoodooMojo Senior Member

    Joined:
    Jan 18, 2012
    Messages:
    344
    Occupation:
    Sr Technical Service Representative
    Location:
    Baltimore, East Coast USA
    M46 w - EDC.jpg

    Verify that when you reinstalled the Control Sleeve no damage was done to the Feedback Pin.
    It is very easy to cause damage.

    You have 900psi at the Charge Pressure Test Point but 0psi at the Servo Test Ports.
    You were moving the adjustment on the Servo of the pump?

    It seems that your EDC is not permitting oil to get to the Servo.
    One of your photos shows the EDC adjustment turned almost completely out.
    If this is still the case then turn the EDC adjustment back in to a working position.

    Either the Charge Pressure Relief is set too high (900psi) or there is internal blockage that is
    not letting the charge pressure relief valve discharge into case drain.
     
  6. davis1676

    davis1676 Well-Known Member

    Joined:
    Sep 28, 2012
    Messages:
    53
    Occupation:
    facilities supervisor
    Location:
    Hooks, Texas
    yeah, I tried adjusting the servo piston from one side to the other ( out of the neutral position) to try and get pressure reading and I also adjusted the displacement limiter back and forth and got nothing. I got fed up with it after my hands got banged up ( boy! it seems when you hit 50, your skin on your hands magically get easier to cut open) and took it to the shop to be sent off. I agree with your opinion VoodooMojo that the EDC is the culprit but I have been working on this thing and neglecting and getting behind on everything else around here. I have to say, I have learned alot just from reading post on this site. Example: you posted about the foot switch having a neg and pos pole and if your switch doesnt make contact with both at the same time you could blow a fuse are ect. I would have never fiqured that out on my own. I appreciate all the help you and others give on this forum. Dont know about Mojo but you should have good Carma. I am a believer in Bad or Good deeds come back to you ten fold. I will post what they find out about it once I hear something.
     
  7. davis1676

    davis1676 Well-Known Member

    Joined:
    Sep 28, 2012
    Messages:
    53
    Occupation:
    facilities supervisor
    Location:
    Hooks, Texas
    well, it has been awhile since I posted. I took my pump to buzzy's repair and he sent it off somewhere didnt tell me where but he said they have done other pumps and know what they are doing. I ended up have the pump rebuilt. Double ouch!! 2,600.00 bucks. I finally had time and weather nice enough to get out and put it on. Long story short is pump is installed and reacts by controller and by manual switch on the side of pump but dont move. Engine pulls down from the load of the pump and the hose down by the distribution block jumps like it has alot of pressure on it but no movement. I know that I checked that brake switch but it acts like the brakes wont release. Should I check the pressure going to the brakes with a test gauge? What would you look for next. I need a push in some direction.
     
  8. davis1676

    davis1676 Well-Known Member

    Joined:
    Sep 28, 2012
    Messages:
    53
    Occupation:
    facilities supervisor
    Location:
    Hooks, Texas
    ok, I got the machine moving. The pump was out and after I got the pump rebuilt the brakes were not getting any pressure to them to release. I replaced all the valves in the hydraulic divider box and bingo its working. thank you for the help on this forum.
     
  9. VoodooMojo

    VoodooMojo Senior Member

    Joined:
    Jan 18, 2012
    Messages:
    344
    Occupation:
    Sr Technical Service Representative
    Location:
    Baltimore, East Coast USA
    Sorry I missed your last post..

    I am glad you got it up and running.
    Run it like you stole it (or rented it).
    Aerial platforms don't like to lay dormant for too long so if it sits a spell take it for a spin every now and then.
     
  10. davis1676

    davis1676 Well-Known Member

    Joined:
    Sep 28, 2012
    Messages:
    53
    Occupation:
    facilities supervisor
    Location:
    Hooks, Texas
    thanks for all your help and everyone else on this forum.