potato gun fun

just woundering if any of you guys built a potato gun or not. my friend and i tried to build one. well we tried to improve his brother's potato gun. the gun they built was built like a bazooka. it consisted of a 3-piece connecter of pvc. one end had a big combustion chamber, the other had a long barrel, and the bottom piece had about a foot long of pipe where the BBQ igniter was. they tried it and it didn't work. my friend and i modified it alittle. we had to cut the combustion chamber in half becuase it was too big. i think another problem is the part the BBQ igniter is on. thats too long and adds to the size of the combustion chamber. we had to stuff a paint roller into the barrel because the potatoes we used were small. it worked alright when we tried but after awhile it stopped working. we checked the igniter and there was a white film over wires that make the spark. it might just be because the wires are old but i think its the fuel we are using. we are using brute... a spray deoderant. i think some of that is getting on the wires and clogging them up.