Need help on small sprayer

Discussion in 'Mechanic and Repair' started by jjreagan, Apr 24, 2005.

  1. jjreagan

    jjreagan LawnSite Member
    Posts: 1

    I have a small 55 gallon sprayer with a 2 hp B&S engine turning a Hypro 4101 roller pump that i use for weed spraying. The old roller pump went bad, so i replaced it with ta new one that is the same size. My problem is that now the engine dies after the pump begins to build pressure. If i disconnect the spray gun, it runs, as this relieves the pressure. I cant figure out why it is doing this, Any help is much appreciated!
  2. Travis Followell

    Travis Followell LawnSite Silver Member
    from KY
    Posts: 2,207

    Is the engine running at full throttle? Will it start back after it dies or do you have to release the pressure before it will start back?

    Their may be a problem with the govenor on the engine. When the load on the engine increases the govenor should open up the throttle to maintain the engine speed. Check all the govenor linkages to be sure they are all in good condition and are working properly.
  3. mike76

    mike76 LawnSite Member
    Posts: 27

    It sound like the bypass circuit on the punp is stuck or not hooked up right. Check the manual on the pump to see if the plumbing is right, and if is check the bypass valve to see if it stuck.
  4. fixer67

    fixer67 LawnSite Silver Member
    Posts: 2,100

    I second that. The old pump may have had the bypass built in and the new one does not even have a bypass and is meant to have a bypass added by the end user (you). I seen this same thing happen last summer. The old pump the man had had the bypass built into the pump itself and the new one was a pump only with no bypass (AKA- unloader). He had to buy a unloader valve assembly and have it plumbed in. It is not uncommon for after market pumps not to have unloader valves in them because that way the pump can be used for more applications. Check the paper work that came with the pump and see what it says about bypass valves or unloader valves.

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