Pete,

Filling the on board or off board tank you hold the Power Max upright, there is a clunk in the Power max can. You want to put liquid in the onboard tank. Make sure your on board tank is vertical. Let the on board tank warm up before you use it. It will be cold when it is first filled. Vapors form at the top of the onboard tank when the tank is warmed and that is what is fed into the engine. From a full tank a little liquid is inevitable at first.

Bob