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im trying to make a potato gun with a spark plug from a car peizo electric lighter and metal container. ive tried it in pvc but the park plug will not ignite hair spray. i get a good spark but still no ignition. will it only work when the flammable gasses are compressed?

A car piezo electric lighter?

I thought all car lighters were of the "hot wire" type...

sorry its kinda worded wrong there its a cars spark plug and a peizo electronic igniter

Most likely problem: too much hairspray

Other possible issue: too small a spark gap - you should aim for about 1/4" and an automotive spark plug usually has a much, much smaller gap.

Thus; maybe make the gap larger.

I think that if you meter your fuel a lot of problems will be solved too

99% chance there is to much fuel
0.99% chance there is to little fuel
0.01% chance that the spark is to small

too much fuel, or too little fuel, also what kind of hair spray are you using?? It has to be aerosol type. Usually, a good 3 second blast should do the trick. good luck and welcome!!

Best method i have found to be pretty much fail safe is to use the humble spark igniter for a gas BBQ or gas oven...
*run the 2 wires down to 2x 5mmx 25mm bolts with nuts and washers.. o-rings aswell if you are anal about leakage..

*drill the small holes in the sides of combustion tube at say 10 and 2 o'clock....insert bolts, nuts, washers, o-rings, do them up tight preferably in a double wall..

*on the insides run 2 short lengths of copper wire... insulated.. un-insulated.. whatever you have... i found thicker to be better but it needs some flex.....

*breech load via a back screw cap.. used to shoot a lot of tennis balls.... *adjust the internal wires so they are in the MIDDLE of the chamber, give it a dry fire to test the spark.. you should get atleast a 3/4 to an inch arc.


the reason i adjust the wires to the center of the combustion tube is to get a better burn.. trust me it works way better this way.

Fuel... i found least to be best... 'Start Ya Bastard' is the shiznay but BBQ LPG is better just squirt a bit in...screw on cap.. point and fire.

hope this helps some.

I wanted to use a spark plug as i have a couple on hand. i gaped them to as wide as they go and still make spark them closed them alittle to insure spark everytime. i use aquenet hair spray. i also used ether with a very short burst and that didnt ignite. so im still at a lose. but its late here so i have to stop work on this for the day. i might just go back to working on my dirtbike. but i will update with well updates from time to time

http://www.spudfiles.com/forums/how-to- ... 22301.html

fuel metering does not have to be complex and should solve your problems.

Try using a small spark plug off a RC engine and use a lighter refill valve epoxy in a small hole on the chamber so you can just use lighter aerosol refill gas, just one or two quick burst with the gas, you won't loose any gas that way

Try using a small spark plug off a RC engine and use a lighter refill valve epoxy in a small hole on the chamber so you can just use lighter aerosol refill gas, just one or two quick burst with the gas, you won't loose any gas that way

I've had a LOT of spark gap problems. usually the issue was me having too small of a spark gap. Might be too much fuel though.

Try spraying your fuel for a full 3 seconds without getting fuel on the electrodes. Get rid of the spark plug as well, you do not need it!!!