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belt driven pump problems STILL!

Discussion in 'Fisher Engineering Discussion' started by BoulderBronco, Nov 29, 2006.

  1. BoulderBronco

    BoulderBronco Senior Member
    Messages: 233

    I posted a couple months ago about the plow not raising once warm unless I am above 1500 RPM. Well I am below 1500RPM 90% of the time so it's a real PITA. Anyway a few of you were pretty sure it was the pump. So I got another (used Ebay) pump that was suposedly good and I have the exact same problem. So I am thinking the pumps are probably fine and there is another issue. Any ideas? I have tried adjusting with no luck.
     
  2. Big Dog D

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


    Try to locate a smaller dia. pulley, it will make the pump turn faster even at the lower rpms. Kinda like a ten speed bike.
     
  3. Bruce'sEx

    Bruce'sEx Senior Member
    Messages: 873

    Could be valve control, maybe not opening fully?
     
  4. Proscapez LLC

    Proscapez LLC Senior Member
    Messages: 293

    does your fisher have a filter in the line?
     
  5. BoulderBronco

    BoulderBronco Senior Member
    Messages: 233

    I am not sure you can do that. I have heard you can blow the pump that way. Also where in the world would I find a smaller pulley for that?

    I have checked but I will check again. Maybe it's just bad

    Nope. No filter.
     
  6. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

    I have never seen a used pump that was really good. The best wayt o tell is to put a pressure guage on one of the angle hoses. All you need is a guage and a coupler about $30 total.

    I buy belt drives off ebay all the time and 95% the pumps are shot, they still work but not well. I have never bought a bad valve and only seen a couple that were seized.

    Disconnect your control cables and grab the valve end with pliers to see if it is moving all the way.
     
  7. plowinginma

    plowinginma Senior Member
    from MA
    Messages: 326

    fisher plow pumps are supposed to have the same size pully on the motor and the pump ..
     
  8. BoulderBronco

    BoulderBronco Senior Member
    Messages: 233

    I will try that with the pliers. It's going to be seriously cold (single digits) tomorrow so I will wait until it warms up a bit. Both the pumps I have work the exact same. Do you know what kind of pressure I should be getting? Also does the fluid heat up if the plow is not used? Meaning if I drive the truck for 20 minutes without using the plow will the fluid still heat up? I would like to check the pressure when it's hot like when using the plow.

    ????
    Not sure what you mean there. The pump is the only thing I have. It's run off the engine so there is no "motor".
     
  9. snoking

    snoking Senior Member
    Messages: 161

    your pump seals are shot, when fluid get warm it thins and slips past the seals inside pump which decrease pressure and flow.

    the only other possibility it would be is your pressure relief stuck open


    only two choises..i see it all the time in the systems that we run on out trucks
     
  10. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

    Yeah the fluid will warm anytime the pump is running if the pump is turning. The Fisher valve is open meaning the fluid constantly loops until needed. This is why a stuck valve will cook a pump. Make sure the valves center thrmselves and that you get full movement.

    Fisher wants the pump turning at the same speed as the motor thus the same size pulley as is on the crank of the motor. I have run 1/2" smaller pulleys on the Pumps with noticable improvment and still gotten good life out of pump. Make sure you use a filter. I also run the return line out in front of the radiator inside the grille when I can. Really helps cool the fluid.

    A new pump should put out 1700-1800psi at 1500rpm. Really you should see at least 1200-2400 at idle on a used pump. Anything below 1000psi is no good.
     
  11. BoulderBronco

    BoulderBronco Senior Member
    Messages: 233

    Well I checked my valve adjustment and it's right where it needs to be. I just thought of something though. I have a custom pulley setup. It is not driven off the crank. It's driven off a 6" pulley which is driven off the power steering pump. So I am thinking that being it's driven off a 6" pulley it may be turning slower than the engine itself. So with that said I have a question that maybe I'll post a different thread about. The pump setup I have is driven off the engine. I am not familiar with the electric motor driven setups. Is it as simple as getting a Fisher electric motor and bolting it to the pump/reservoir I currently have? I guess what I am saying is are the two setups the same just depending on which way you set it up? Or is the reservoir different for each setup? I am trying to figure out options here because this really sucks. I have also been searching for a smaller pulley with no luck. Any suggestions?
    Thanks
     
  12. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

  13. BoulderBronco

    BoulderBronco Senior Member
    Messages: 233

    Right. But my belt system is different as I mentioned. I measured my pulley and it's 4.75". Now suposedly there are three pulleys available, 6", 4.75" and 3.75". I found a 3.75" (P/N7946) pulley but it's $90. If you have one smaller than 4.75" that would surely help. Thanks.
     
  14. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

    You can buy a new pump pulley for $20 at any Tractor Supply or from any catalog. The have lots of universal sheaves as they are called, just match up the shaft diameter. I may have to 3.75" but most came with the 4.75".

    I was talking about having a Ford crank pulley, but that may not work if your whole system is different. Let me take a look at what I have and if I don't I will direct you to the right one.
     
  15. BoulderBronco

    BoulderBronco Senior Member
    Messages: 233

    I did some online searching of tractor sites and didn't find much. Do you know of anything specific? Your right about the crank pulley. It will not work with my setup. I am running an aftermarket air compressor system. The compressor runs off the P/S pulley. My pump then runs off the air compressor pulley (dual 6" V-belt pulleys). So if you can come up with a 3.75" pulley for my pump that would be sweet.
    Thanks for all your help.
     
  16. Flipper

    Flipper PlowSite.com Addict
    from CT
    Messages: 1,180

    Check the shaft diameter of the pump but something like this will work.

    http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611578168 If you can't find the right diameter you may need a bushing to make it work.

    or look at this page at Grainger.

    http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611578168

    Looking for a 4L or A Belt. Locally a good hydraulics, power transmission or Farm Machinery supply like Tractor Supply should have what you need on the shelf. Maybe there is a Grainger near you.
     
  17. BoulderBronco

    BoulderBronco Senior Member
    Messages: 233

    I got one of those today at my local hardware store. They do not make a 1/2 bore pulley with a keyway so I had to notch it myself. Pretty easy. It is also fatter than the stock Fisher pulley because of the set screw, so I may have to grind it down a bit. Other than that I think it will work fine. I got a 3" pulley. I think that it was better than a 3.75". A 3" will spin 37% more where as the 3.5" would only spin 26% more. So even if I am running at 3K RPM the pump will only be spinning around 4100 RPM. I think the pumps can handle up to 6K and I won't even be close to that. Thanks again for all your help.