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Older Hyd MM1 seems weak

Discussion in 'Fisher Engineering Discussion' started by fisherz71, Jan 27, 2013.

  1. fisherz71

    fisherz71 Junior Member
    Messages: 6

    I have a belt drive hydraulic MM1 7'6" on a 92 k2500. I have had this plow for 7 years and its been bulletproof reliable. Last year I put on a new fisher A2311 pump because it was slowing down when it warmed up.
    This system is not known for its speed which is OK but my issue is with its lack of power. It can stack snow if I time it right,but if I try to raise the blade with any amount of snow, it won't lift the load. The angle rams are no better. I can push snow all day but the hyd always seem weak,I think it should be able to lift more. I had a old 85 Ranger with a small Gresen(?) pump that would always lift the plow or flatted out the F150 coil springs. This has always been my only complaint my this plow. Am I asking too much from this pump or is this the way they perform? Is there anything I can change or adjust?
    The pump pressure tested good,I have put new o-rings in the control valve,the spools move fully and the belt is tight.
    Thanks in advance for any replies....Brad
     
    Last edited: Jan 27, 2013
  2. RepoMan207

    RepoMan207 PlowSite Fanatic
    from Maine
    Messages: 5,035

    A few things come to mind; the controller is getting worn out, the cables need adjusting, and do a pressure test. It should be within 1400-1700.
     
  3. fisherz71

    fisherz71 Junior Member
    Messages: 6

    I pressure tested the pump and it was good, the cables work good ( I even unhooked the cables at the control valve and manually applied the spool valve), and you said a "worn controller", do you mean the control valve?
     
  4. Big Dog D

    Big Dog D PlowSite.com Addict
    Messages: 1,134



    When you changed out the pump did you put a different pullly on it? If you did swap out the pulley for the old one. The pullley size affects the rpms of the pump and thus the volume of fluid it will push.
     
  5. fisherz71

    fisherz71 Junior Member
    Messages: 6

    I reused the old pulley on the new pump. My next step will be to retest the pump pressure to the control valve, out of the control valve and to the rams to see if there is a pressure loss.
     
  6. fisherz71

    fisherz71 Junior Member
    Messages: 6

    Retested the pressure from the pump,from the control valve and at the lift ram. When cold the pressure maxs at 1700psi. After an hours running it drops under 1600psi which seems good. But after an hour I can notice the angle/lift speed has slowed. I have the psi gauge hooked up in before the control valve now so I can check the psi anytime. After a 1 1/2 hour run the psi was at about 1600psi max. I tried both the lift ram and angle rams and noticed this: the lift ram and left angle showed 600psi with rams operating (seperately of course) while the right angle showed only 100psi while angling (with no difference in speed/power). When fully extended all 3 functions still maxed at 1600psi. I am out of ideas...anyone got anything to add?
     
  7. Big Dog D

    Big Dog D PlowSite.com Addict
    Messages: 1,134

    Add a smaller diameter pulley. Doing so will cause the pump to spin faster delivering more flow at lower rpm's.
     
  8. tractorbill

    tractorbill Member
    Messages: 65

    Replace the couplers, had several units act like yours.They might look fine but, replace them and try it.
     
  9. fisherz71

    fisherz71 Junior Member
    Messages: 6

    To TRACTORBILL: by "couplers" do you mean the quick connect fittings?
     
  10. tractorbill

    tractorbill Member
    Messages: 65

    yes, I have had them work ok when the fluid is cold and thick and then partially close up when warm.
     
  11. fisherz71

    fisherz71 Junior Member
    Messages: 6

    Thanks for the reply, I will try a new set of quick connects and see what happens.