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Old Fisher plow, pulleys and pressure queries

Discussion in 'Fisher Engineering Discussion' started by uglytruk, May 15, 2005.

  1. uglytruk

    uglytruk Member
    Messages: 74

    On my '86 'Burb 6.2, the plow looks to have been dealer (properly) installed. I havn't used the truck much, but I did notice that the plow moved very slowly, unless I raised the idle. I wonder how to check pressure, and if the pump is turning too slowly. The pump runs off of the fan, with a rather small dia pulley. This slows things down compared to my large (fan/drive) pulley on my '83 305. But the pulley looks "right". Whats' a pump cost? Rebuild or new? Do it myself? Any suggestions?
     
  2. justme-

    justme- 2000 Club Member
    Messages: 2,138

    after adjusting the packing for the cylinders it should move better but remember it will always be slower at idle than above idle. The pump rpm affects the flowrate (not pressure), and there is an upper limit to pump rpm. If the engine redlines at 5K and the pump max rpm is 2K you need a reduction in the pulleys so the pump never goes over it's max- hence the idle speed is slow. If you have the factory pulley on the pump, and it is mounted where Fisher says to mount it with the pulley on the engine the one Fisher says to use don't worry about it- it is what it is. that is the drawback to engine pumps, but it saves the electrical system big time.
     
  3. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,569

    leave the cyl packing alone if there not leaking.... smaller pulley=higher rpm..
    does your system have an filter? if so cheek it and clean. and change the fluid, yes, rpm will effect the pressure and the flow rate. ( there related ) more flow-more pressure..
    It will work fine with a little practice, start to lift the blade as you run in to the pile and stack the snow should help with faster cycle times.
    Does your truck need an tune up? an poor running engine will be pulled down by the load of the pump trying to lift the blade.
     
  4. justme-

    justme- 2000 Club Member
    Messages: 2,138

    I agree with your tips on lifting the blade as your driving- should be normal practice for any type of blade tho.
    There was a post (now aparently deleted before mine) relating to packing- seems the lift cylinder packing could be too tight and binding the ram.

    Plow and pressure are related, but increase in RPM on a system with no resistance only increases flow- pressure only builds (beyond negligible amounts) when there is resistance. The pressure will increase when the blade comes off the ground due to increased resistance, but the flow rate is what is doing the speed injustice. More flow means more oil in the lift ram faster. Same principals as a log splitter- retracting the ram it's the flowrate that pulls it in quickly so you can get a new log in there, flow gets the ram to the log quickly (cycle time), the log creates resistance which slows flow rates and increases pressure until the resistance is decreased.
    As long as the dealer installed the plow system do not change your pulleys unless you are absolutly sure of the rpm changes they will have. You don't want to be replacing a pump because you overspeeded it with a poor pulley selection.
     
  5. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 8,569

    I just hate those pesky deleted posts!!!! :redbounce As you can see a deleted Post can lead to an misunderstanding too..
     
    Last edited: May 18, 2005