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Fisher speedcast dropping

Discussion in 'Truck & Equipment Repair' started by Toady, Oct 23, 2009.

  1. Toady

    Toady Junior Member
    Messages: 9

    Hey guys, any thoughts? I'm new at plowing. Have an old fisher speedcast on a 92 GMC 3/4 ton truck. The plow won't hold the up position. It creeps down to the ground in just a couple minutes. The pump seems to lift it ok, it just won't stay up.
    I replaced the lift cylinder but no better. I have to assume it's the valve assembly. I have been searching these posts and found a link to Northern Equipment where I can buy a HALDEX pump/valve combo with the switch for about $650. I don't want to do that, then find out it was something else. Is there something else that could cause this? I can't find any leaks.
    The valves are expensive, and I may need a new cable as well.
    The PUMP seems to work fine. Is there a way to replace JUST the valve with an electric set-up (in other words keep the fisher pump) Basically like the Haldex but without the pump portion of it
    Thanks for any help Guys.
    Toady
     
  2. Toady

    Toady Junior Member
    Messages: 9

    I spoke with a local installer (dealer but not of fisher) Wants me to bring it in Monday and have him look at it.
    .
    If it's creeping down, but not losing fluid, and the cylinder is new. Should I assume it has to be the valve body? I'll just eat the 650 if I have to and buy this http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_613_613 if I can be certain it will solve the problem.
    It has 1/4-18 NPT thread. Will that fit the fisher hydraulic lines?
    Thanks for your HELP
    Toady
     
    Last edited: Oct 23, 2009
  3. theplowmeister

    theplowmeister 2000 Club Member
    from MA
    Messages: 2,552

    Might be just a valve need replacing or presure relefe valve leeks
     
  4. Toady

    Toady Junior Member
    Messages: 9

  5. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    The reason you don't see leaks is because it leaks internally. I know the old cable operated Fisher valves will do that (I have one that does it), and there is nothing that can be done to fix it. You don't have much to lose at this point by dissassembling yours. It's possible you have a piece of debris stuck in the valve seat preventing it from closing fully.

    At the end of the day, that new unit might be the way to go. Maybe you can sell your old pump to offset some of the cost.
     
  6. Toady

    Toady Junior Member
    Messages: 9

    Good point, If I'm gonna spend the dough on that unit, I'll try taking that old valve apart first, and see what I can do with it. Thanks,
     
  7. GPS

    GPS Senior Member
    from MA
    Messages: 268

    I've seen that problem due to cable adjustment also. If the valve is slightly opened when the control lever is in the centered position, you'll get the same symptoms as an internally leaking valve. Disconnecting the lift/lower cable from the valve will verify if it is a cable problem or not. If you manually open the valve to lift the plow, and then let the valve center, it should stay up. If it leaks down then, the valve is leaking.
     
  8. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Toad - is your valve manifold actuated by cable or electric solenoids?
     
  9. Toady

    Toady Junior Member
    Messages: 9

    It is the old CABLE style. Even without tension or pressure on the cable it still leaks down.
    So, I'm going to take YOUR advice and pull apart the valve. Not sure what I'll find. But I'll try to clean it and reassemble it. If that does not work, I may go with the HALDEX system. I can find used parts on craigslist, but chances are that it would be another bad valve if I bought one without being able to test it somehow
     
  10. GPS

    GPS Senior Member
    from MA
    Messages: 268

  11. Toady

    Toady Junior Member
    Messages: 9

    there's a few used ones for 50 bucks or so, but don't want to take a chance on a used one, and get stuck buying another junk one.
    trying to get hold of the guy on ebay now.
     
  12. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    You can still buy a valve body from Fisher for engine driven pump systems. Have you tried them to see if you can still buy the valve body you need?
     
  13. Toady

    Toady Junior Member
    Messages: 9

  14. GPS

    GPS Senior Member
    from MA
    Messages: 268

    I can't say that I have any experience with those units. From what I can tell, Haldex is the same company as Barnes, which is a very well respected hydraulics company. I doubt it would be a bad choice. It would likely speed up the plow operation some, too.
     
  15. bguzz

    bguzz Junior Member
    Messages: 7

    I think you can replace the o-rings in the valve body when you take it apart...that what is most likely leaking. Before you do anything though, try adjusting the cables that the valve unit...that may be the problem. But I would be you have worn o-rings.
     
  16. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    I have been told the O-rings only keep fluid from leaking externally. Never taken one apart, so I could be completely wrong.
     
  17. Toady

    Toady Junior Member
    Messages: 9

    Pulled apart the valve. I can look down and only see the 2 O rings on either end, which appear to only stop external leak. There are 2 also 2 very small grooves on the valve, which look like they could hold very small O rings in them, but there are none, I'm trying to determine if there are supposed to be O rings in there or not.
    Thanks to all for the help
     
  18. Toady

    Toady Junior Member
    Messages: 9

    Anybody know if there should be O RINGS on the shaft itself?
     
  19. 2COR517

    2COR517 PlowSite Fanatic
    Messages: 7,115

    Sorry, I don't. Someone should pipe up soon.
     
  20. gypyscatfish

    gypyscatfish Junior Member
    Messages: 4

    It seems to me if the pump will raise the plow the pump should be ok. If it leaks down i think it has to be the valve leaking. If it is slow to rise and and leaks down it could be a combination of weak pump, too big of a pulley,AND A LEAKING VALVE. I have looked everywhere and yet to find any info as to what can be rebuilt or adjusted on the valve body. I put new o rings and no luck. I do not want to replace the pump and the valve body, the truck is not worth it. Has anyone done anything to the valve body other than adjust the cables so plungers sit in the detent after lifting plow and replace the o rings? There must be someone who has solved this problem somewhere. If I take mine apart again, I will take pictures and post what I find.