SpudFiles

I just made my first potato gun but... it only shoots with propane and nothing else, what could be the problem?

Is it metered? Do you have any pics? What other fuels have you tried? We need more information to help you.

No one on the forum can even diagnose the problem if you are not more specific.

Pictures always help too.

The only thing I can go by is that you are not fueling your chamber correctly. Please use the search function to figure out how to properly make a fuel meter.

i have tried various things like hairspray, starting fluid and axe, but they rarely work and its not metered

You're spraying too much or too little or your spark is not big enough. Try adding a chamber fan too. That will help.

Check your fuel. Some brands don't burn nearly as well as others.

Search for hairspray flame-throwers to see how to test them for flammability. Do this outside and use a candle instead of a lighter. No need to burn yourself testing fuels. Be safe.

ok, thanks, ill try these things when i get the chance

As long as you have a spark, it should fire dude!! How big is your chamber?? ON my spray and pray, My chamber is 20" X 3"... I spray aqua net hair spray for a full 4 seconds, and it works every time. After a while, you should be able to tell just by looking in the chamber if you have too little or too much fuel!! My bet is that you are using way too much!! Good luck!!
Just seen the pic of your cannon. That chamber is small, you should only need like a 2 second blast of hair spray, and get that cap on fast!!!! Where is your sparker located????

Propane sinks, it's heavier then air. Are you holding your chamber up and dumping in the propane? Or just holding it level???

wait longer after ignition?
more ignition or fuel?
what fuels have you tried?

Carb cleaner works good !!!!

But chamber looks kinda small

might need a longer barrel there too bud

In my experience, the easiest sure-fire way to get a spray-n-pray to fire consistently is to load it after fueling it. However, this can be dangerous if you cannot disconnect your ignition. I used to use cheap $1 cans of clear coat for fuel because it has excellent power and is much easier to fuel with. I have put golf balls about a quarter mile (roughly 500m) with a massively over-sized gun. I would have posted it but I don't have this one anymore. I may have a video somewhere though so stay tuned!

Mr.Tallahassee wrote:In my experience, the easiest sure-fire way to get a spray-n-pray to fire consistently is to load it after fueling it. However, this can be dangerous if you cannot disconnect your ignition. I used to use cheap $1 cans of clear coat for fuel because it has excellent power and is much easier to fuel with. I have put golf balls about a quarter mile (roughly 500m) with a massively over-sized gun. I would have posted it but I don't have this one anymore. I may have a video somewhere though so stay tuned!

You shot golf balls using combustion> dont you need an air tight seal?

I wrapped them in duct tape. I probably should have added that. I made them fit tight enough that they acted somewhat like a detent or a burst disk. I had to actually use some force to fit them into my barrel. I guess I'll give some specs too. The chamber was 5' of 3'' PVC and the barrel was 5' of 2'' SCH80 PVC. I sprayed my cheap paint with it unloaded until vapor came out of the barrel. Then I capped it and loaded the golf ball. I'm digging for a vid still.