Some friends and I tried to blow up a van with, among other things, gasoline vapors. Getting a van from a wrecking yard, the plan was to have an explosion for a rock video (Stone Cold Bitch by Silveroad). This is the video, the van burns at around the 4:16 mark.
Now, the plan seemed simple. The van was liberally splashed with gasoline inside. We had four or five airbags placed in the interior; on the seats, in the back cargo area and by the dash, and on top of each airbag was a big cup full of coffee-mate. We knew how well coffee-mate burns when you pour it over a flame.
One airbag test, we put it under the hood and connected it to a car battery. Boom! It went off hard enough to bulge the hood up several inches, a lot of power!
After waiting until it got dark (didn't take long, it was almost winter and we were freezing) we got ready for the video. So with the gasoline in place, on the count, the airbags would be set off with the battery and for extra measure (and red glow) someone ran along the far side that was out of the shot and threw in a lit road flare, y'know, just to make sure. Countdown, and...NOTHING! The airbags wouldn't go off. And the van full of gas didn't catch fire. We stared at each other for a few seconds, then someone ran over, reached in and grabbed the flare.
We studied the battery connections, couldn't figure out why none of the airbags ignited. They should go off with a hint of power. Well, not taking any chances, we rewired them all so that they would get direct 120 volt current plugged into a long extension cord. We tried the scene again.
This time, the flare caught the gas on fire. The plug was inserted, and...still nothing. The lights went dim like we were drawing a lot of amps (I thought the breaker would pop) and finally after a couple of seconds the bags went off and we got the shot in the video.