[Jon Salem]

Thanks. Make sense. Looks like the pumps have two one-way valves. The manual has nice pictures. A simple test I may try : run engine and let cool. Cover carb with clear plastic and plug canister hose. Let sit 3 days. Check plastic for vapor condensation. Remove plastic and plug. if the motor start quickly, then evaporation is the issue. If not, it must be running back to the tank....................The system seems sealed.....I can email the pictures and text - they are a bit large to upload.