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Fisher plow problem

Discussion in 'Commercial Snow Removal' started by gmc93, Jan 15, 2005.

  1. gmc93

    gmc93 Junior Member
    Messages: 9

    Just got a truck with a Fisher plow on it. The plow was used about ten times a year and sat idle for one winter before I got it. There are two problems. One is that when the hydraulic fluid is warm, I have to rev the engine over 3000 rpm's to raise the blade. When the fluid is cold, the blade will raise with the engine idling (pump wore out?). Both angle cylendars are sluggish too. When I lower the blade, it drops like a ton of bricks. I'm no expert but this doesn't seem right. The other problem is that the blade will not stay up. Once again, not a problem cold but when warm, I have to pull over, put the truck in park and rev the blade up about every two miles. When idling, the blade will actully lower when I try to raise it. We're expecting another nor'easter tomorrow night and I'd like to have this problem fixed by then if it's possible. Are there any adjustments that could cause and cure this problem?
  2. ksland

    ksland Senior Member
    from ma
    Messages: 419

    Bad pump, mine did the exact same thing. Replaced the pump ($140 if I remeber right) and it worked perfect afterwards.
  3. cet

    cet PlowSite Fanatic
    Messages: 7,257

    I would first check the fluid level. It sounds like it is low.
  4. ksland

    ksland Senior Member
    from ma
    Messages: 419

  5. gmc93

    gmc93 Junior Member
    Messages: 9

    Forgot to mention that I made sure the pump was full and I have a brand new belt. I can see how the pump could cause the lifting problem but the blade should stay up with the engine turned off. There must be a valve that controls the backflow of fluid or an adjustment to that valve. Any thoughts on this? Thanks for your response.
  6. ksland

    ksland Senior Member
    from ma
    Messages: 419

    Make sure the valve control is in true nuetral postion by adjusting the cables. Like I said...it is your pump...procrastinate all you want...the quicker you replace the pump the better off you are.
  7. Bolts Indus.

    Bolts Indus. PlowSite.com Addict
    Messages: 1,176


    I shall assume we are talking about an engine driven pump. Hard to diagnose without seeing it but it can be either belt on pully slipping when hot, cable adjustment, or there are o rings in your valve body that are shot or the pump is shot. I am not thinking pump as it lifts when cold. Where you located?

    PS: Upon review of your post I am inclined to believe because it has sat for the previous year that the o rings in your valve body are dried out and leaking.
    Last edited: Jan 15, 2005
  8. harley hauler

    harley hauler Senior Member
    Messages: 214

    I used to run a f350 with a 9' Fisher, and we had the same problem. When you first raised the blade when the fluid was cold no problem, then as the night went on and the fluid starts to heat up you would have to tach the thing out to get it to raise. Also same problem with the blade weeping down as we where driving. So heres what we found after trying adjusting the cables and stuff.

    1. Fluid was from the previous season and was pretty much shot (burnt smell) Bad fluid good in the cold (cause it was thick) bad when it heated up and thinned out. So change out the fluid work alright bit blade would still weep.

    2. To solve the weeping problem we took the vavlebody apart and change the needle valves for your up,down and angle functions. That solved the weeping problem blade the operated like brand new.

    3. Blade drops like a ton of bricks when lowering. If you have a big blade thats alot of weight coming down from the lift position. So on the older trucks with the under the hood hydro's they didn't have the soft drop like all the new fishers, the only way to control it is by how much you push the stick down.

    Like I said this was all tried and tested on our 350 and it worked for us. JMPO
    hope I was of some help. :waving:
  9. gmc93

    gmc93 Junior Member
    Messages: 9

    Fisher snowplow problem

    Thanks Harley Hauler for your advice. It makes sense about the valves. The pump was nearly empty when I got it though and I refilled it, so it's mostly new oil but I think I'll replace all the oil before buying a new pump. When I got the truck it came with a full jug of transmission fluid that the previous owner was using. I just assumed it must be the right kind. I just noticed that it is Dexron III not Dexron II as the manual says should be used. Is there a difference. I feel a little stupid for not checking before but I guess that's part of being a newbie. Live and learn I guess. If the fluid is alright, I guess I'm in for a new pump. Thanks for your help.
  10. lawnmedic

    lawnmedic Senior Member
    Messages: 703

    Dextron III should work fine in your pump since it exceeds all Dextron II specs.
    As far as your problems, my old Fisher plow had similar problems with the under hood system. Leak down was caused by o-rings in valve body. Slow to operate(lift,angle) was caused by worn out pump. Had buddy(machinist) rebuild pump, and no more problems.....
  11. snoluvr

    snoluvr Senior Member
    from RI
    Messages: 266

    I would check the packing nut on top of your lift cylinder as well..it keeps the fluid in but allows movement.if it loosens up, you may have the blade dropping like you described.
  12. Bolts Indus.

    Bolts Indus. PlowSite.com Addict
    Messages: 1,176

    Do not buy a new pump before you check and fix the cheapest part. Always start your repairs with the easiest cheapest parts and work up. In this case it most likely is the o rings in your valve body. $2.00 repair.
  13. wirenut

    wirenut Senior Member
    from nh
    Messages: 529

    older pumps

    what you do with them is cut the tank in half to get at pump
    take pump and have it faced whats happening is there is to much space
    and the oil bypasses.
    i have one sitting on the shelf that i did years ago :drinkup: :drinkup:
  14. gmc93

    gmc93 Junior Member
    Messages: 9

    I'm sure now that I have the two problems that Lawnmedic stated and it makes sense to go the cheaper route first. However, I've never seen the inside of the valve body and don't know where to find the O rings or needle valves. There are some bolts on the front end of the valve body. I'm assuming that's where I go in. Can someone give me a quick rundown of how to do the replacement. I found a parts dealer about ten miles from me. It will likely be Tuesday before I can get the parts if the weather forcast is right (up 45cm of snow with wind gusting up to 100km/hr). Everything will be shut down if this happens. We had a slightly larger storm last February and the only people who were plowing were the payloader operators. Maybe the same thing tomorrow. I want some snow but this is rediculous.
    When I get the parts I'll let you know how things turned out. Hopefully it will be a help to someone else.
  15. justme-

    justme- 2000 Club Member
    Messages: 2,138

    BTW the weeping problem is the valve being worn- I have it on my chevy. This is normal but is accelerated by not useing the cary chain when transporting between sites. It's a PITA to go out and hook the carry chain and unhook at each site but that takes the strain off the valve and helps the seals last longer. It also affects the same way on all plows, reguardless of make (that I am aware of) or weither it;s a speedcast/minute mount etc. The weight of the blade bouncing on the valve....