[texjake]

Originally Posted by FirstOwner69

The easy fix might be to try a cheap check valve out of sight in the supply line between the reservoir and pump. A lot easier than getting to the pump.

Not sure this is the right size or the proper application...does say liquid in the title though.
http://www.ebay.com/itm/Hydrogen-HHO...10571a&vxp=mtr

Found this by searching ebay motors for "check valve". Lots more in various sizes including some for gas and diesel made of aluminum.
http://www.ebay.com/itm/6mm-1-4-Fuel...5f499e&vxp=mtr

Good job! Now that's thinking outside the box. Now why didn't I think of that...lol I'm going to try that and let you know what the outcome is. Thanks!