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Control Valve Problem - Fisher

Discussion in 'Truck & Equipment Repair' started by Craigwell, Dec 15, 2008.

  1. Craigwell

    Craigwell Junior Member
    Messages: 27

    Alright, I have this issue with my older Fisher style setup..

    The blade lifts and angles perfectly, but I cannot get the lift cylinder to lower! I have recently installed this setup on my 1976 F250, and discovered the problem today.

    I don't think it has anything to do with the Cylinder, as the pump does not load up whatsoever when I move the spool in the downward position on the DCV. I have verified that the cable is free, and that the adjustment is proper. The spool moves easily the full range of it's travel, at least what I can see from the exterior.

    Is anyone familiar with this type of valve? Wondering how exactly to repair what I assume is something sticking inside.

    Thank you for any advice. Excellent Site!


  2. Craigwell

    Craigwell Junior Member
    Messages: 27

    it now occurs to me also that the pump wouldn't be involved with the act of retracting the lift cylinder... anyone have any ideas? The sucker hadn't even bled down an inch in 4 or so hours!! I ended up taking the tension off by jacking and blocking up the blade, just to be safe..
  3. grandview

    grandview PlowSite Fanatic
    Messages: 14,609

    Could be an air pocket in the line.
  4. Craigwell

    Craigwell Junior Member
    Messages: 27

    the lift cylinder has only one line at the bottom of it, and it did extend the piston fully when I tried it.
  5. Crash935

    Crash935 2000 Club Member
    Messages: 2,377

    For giggles, try loosening the hose to the lift cylinder and see if it drops, dont take the hose all the way off, just crack it enough to let some fluid trickel out.
  6. Craigwell

    Craigwell Junior Member
    Messages: 27

    Hi there,

    I will try that at each end of the hose.

    Thank you for the suggetions.. I'm working away at a checklist here to put into play for the morning.
  7. no lead

    no lead PlowSite.com Addict
    Messages: 1,308

    if that doesn't work, try loosening the gland nut on the top of the cylinder.
  8. Craigwell

    Craigwell Junior Member
    Messages: 27

    a friend with some hydraulic experience mentioned for me to take a look at the reliefs on the valve as well.

    When I was at Princess Auto for Quick Disconnects the other day; the Hydraulic guy looked at the valve and mentioned the relielfs were "set high".

    I assume this means I want to back the relief for the raise / lower side of the valve out a bit. I'm still looking for a diagram or service manual that mentions how to work on these valves or at least an exploded diagram.

    Thanks again
  9. Niteman9

    Niteman9 Senior Member
    Messages: 165

    Like Crash said crack a fitting on the hose and see if it will drop. Yes means problem in the valve no means problem in the cylinder. I have the same valve on my old dodge and was having problems. Sometimes I would have to race the motor to get the plow to raise with any speed. I took the valve apart and cleaned and lubed it up and change the fluid and have not had the issue again.
  10. Craigwell

    Craigwell Junior Member
    Messages: 27

    I was able to resolve the problem this morning. I cracked the cylinder line at the valve, and nothing happened. Then I backed out the relief about 1/2 a turn, and that did it! Works perfectly now.

    Unsure why it was screwed in too much. I wonder if the guy who sold it to me thought it was toast, hence reason for selling..

    Oh well. $600 later, and I've got a functional hyrid Fisher / Diamond Plow setup!! (Diamond 7.5' Blade, Fisher Hydraulics, Custom Mount)

    Thanks for everyone's assistance.