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Plow doesn't go up all the way

Discussion in 'Truck & Equipment Repair' started by dkunst, Feb 20, 2007.

  1. dkunst

    dkunst Junior Member
    Messages: 4

    I bought a used old plow but don't know the brand. It has a pump and DC motor that mounts on the fender under the hood. It has a control valve for the angling and lift that had control rods into the passenger compartment.

    When I apply the power to the pump, it is a negative solenoid control, it sounds good. The angling will angle the blade on the ground to full reach both ways. The lift cylinder starts to go up, but stops when the load of the blade is applied only lifting a inch or so and then the seems to load down but will not go higher. If I manually lift the blade, and then power it, it will hold the blade in the air and will angle also. The cylinder lowers without an issue and can be moved up and down manually with no leaks around the seals or hoses. I did not change the fluid or know if there is a filter in the system.

    The fluid is full, but I did have the hose of the lift cylinder for installation.

    Any ideas what plow manufacture this is? Any idea where to start to diagnose?

    Does the lift cylinder need bleed and how would that be done?

    Thanks
     
  2. oarwhat

    oarwhat Senior Member
    Messages: 162

    It could be a monarch pump. It sounds like a bad pump or if your lucky dirt in the relief valve. The cylinder doesn't need bleeding. What happens is the pump is strong enough to angle the plow but cannot make the pressure to lift it. If the relief valve is set to low or dirty it will cause the same problem.
     
  3. dkunst

    dkunst Junior Member
    Messages: 4

    Dirty relief

    thanks for the quick relpy. Any guess wher the relief valve at? Do I need to pull the pump apart to clean the valve or is the valve on the side. It has a control on either side that when rotated contacts a ground with a finger that turns on the pump. One of course has two contacts on the other one. Any idea what kind of pressure it should genertate?
     
  4. oarwhat

    oarwhat Senior Member
    Messages: 162

    You will have to post some pictures before anyone can tell you what pump you have and how to fix it.
     
  5. dkunst

    dkunst Junior Member
    Messages: 4

    Pics

    hope this helps identify the pump

    HI Saipan 0207 pics camera 054-3.jpg
     
  6. oarwhat

    oarwhat Senior Member
    Messages: 162

    That's an awful picture but, it looks like a monarch. I have'nt worked on one for a while. The silver part under the valves is the hydraulic pump. On the outside of that there are some nuts with valves behind them. One is the relief valve and the others are check valves etc. (don't remember them all). You can remove and check for dirt or something stuck in there but don't change anything put them back exactly as they were. I might have an old service manual I'll look when I get a chance.
     
  7. dkunst

    dkunst Junior Member
    Messages: 4

    update

    You were right it is a monarch, not sure if it is a 304 or M500 3,4 way.

    I pulled the reservoir off and cleaned the filter. There was some residue in the tank, but I don't know if it has ever been cleaned out. No major chunks, but there was what could be filings/shavings. I also took out the relief valve and pumped fluid through it.

    According to the drawings, there must be many configurations internally. Mine only had a filter tube inside and the return tube coming through the tank.

    Put it all back together and no change, the lift only takes a load and then stops. The motor bears down. No leaks, clean fluid. The lift cylinder looks pretty new.

    Unless I missed something, sounds like the pump itself is bad. Can they be rebuilt or even replaced as old as it is?
     
  8. oarwhat

    oarwhat Senior Member
    Messages: 162

    I haven't fixed one in a long time but I'm sure someone has replacement pumps. Did you try turning the relief valve up? Maybe hookup one of your angle hoses to your lift cylinder. If it lifts the plow there is something wrong with the lift circuit. I know we went though quite a few pumps. Make sure you use a quality fluid in the unit. We ruined most of our pumps by using off brand fluid.