Hypro d403 driving me nuts!

Discussion in 'Pesticide & Herbicide Application' started by philk17088, Jul 19, 2008.

  1. philk17088

    philk17088 LawnSite Fanatic
    Messages: 17,386

    I replaced the diaphrams in both my space savers along with O rings. Now both pumps seem to be cavitating all the time. The pressure gauge needle jumps up and down and all the hoses shake wildly. I have torn both pumps down twice and still cannot cure this. The manual that came with the pump is no help.
    Any ideas?
  2. bug-guy

    bug-guy LawnSite Bronze Member
    Messages: 1,033

    make sure the o-rings are seated prroperly the d 403 has had some problems with the metal getting pitted and it makes it hard to seat the orings.
  3. LawnTamer

    LawnTamer LawnSite Gold Member
    Messages: 3,986

    There are little spring valves in the cylinder heads on the d403, they can just fall out of the head when rebuilding. Is it possible that one or more is in backwards? They will go on backwards.... learned that the hard way I did.
  4. philk17088

    philk17088 LawnSite Fanatic
    Messages: 17,386

    ummm... how do you tell which is the right way?:eek:
  5. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,814

    My Lesco man (store 502) explained, how on my Hypro D-252, you need to put about 15 pounds of air in the top above the damper diaphragm. This greatly reduced my needle bounce in the pressure guage.

    How much pressure are you running? Is it excess?

    Is your pressure regulator valve or seat worn?

    Possibly only one side is working due to a bad valve. Whole new valves are only about $15.
  6. turfman07

    turfman07 LawnSite Member
    Messages: 52

    sounds like your sucking in air from somewhere. i had one do that to me and had to change the suction filter housing gasket.
    just a small air leak on the suction side will make those pumps act haywire.

    makes you want to throw it in the trash and buy a piston pump.
  7. heritage

    heritage LawnSite Bronze Member
    Messages: 1,358

    This is the advice to follow, if all was well b 4 the rebuild.

    Look at an "Exploded View" of the valves.

    Seat may be upside down.

  8. bug-guy

    bug-guy LawnSite Bronze Member
    Messages: 1,033

  9. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,814

    Did you say cavitation? Could be a suction problem, like Turfman said. Clean the filters and tank to filter hose. Install new gasket on filter. It is best to use 3/4 inch clear vinyl hose for this area. If it collapses due to suction--you know it is time to clean the filter. Be sure the free gravity flow from the tank is at least double the gallons per minute you are trying to get out of the spray nozzle. Check inside the tank for residue or obstruction. Years ago we had a truck that never sprayed right. Turned out a tech had dropped a white spray nozzle into the tank--and never told anyone. The nozzle would periodically get caught in the tank outlet fitting--pressure would drop to about 25 pounds. It was weeks before our mechanic found the problem.
  10. philk17088

    philk17088 LawnSite Fanatic
    Messages: 17,386

    THe d403 doesn't have the air chuck.
    I am thinking it's the valve seats.

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