SpudFiles

I have two potato cannons made of ABS they have 14 to 16 inch combustion chambers with approximate 5 foot barrels they are ignited by scavenged BarBQ igniters and fueled with hair spray. I havve found first that neither work well (beyond a single shot) in a Canadian winter. I attribute this to condensation providing a connection between ground and sparker along the inner surface. I tried widening the gap a the entry point with little improvement. The real problem is with the smaller bore gun it is only good for a shot or two and often misfires although visually exhibiting a good spark. I am a Newbie with a primitive system by your standards after looking around but need advice. Sponge Bob

Your gap should be a 1/4 inch and you are probably using too much hair spray. Try a 2 to 3 second squirt of aqua net hair spray. Must be aerosol and not the pump kind. good luck..

Trying Carb cleaner or propane measuring

Misfiring only after a successful shot suggests that your aren't adequately purging the combustion gases from the chamber between shots.

Also, at low temperatures fuel mixing is pretty slow. Add a chamber fan or simply wait a minute or two after fueling.

Metering will also help a lot.