Hmm, this wouldnt have anything to do with GLP would it?
What those crazy folks do on carriers, I don't know. But letting fuel pool in an engine and then lighting it is a bad thing in the civilian world. It will at least shoot a flame and possibly explode. Maybe carrier pilots do it or used do it, but I'd like to think they are a bit more cautious than that.
That said, it's been done accidently by say motoring the engine, opening the fuel valve and then remembering that you forgot to turn on the ignitors or one system is failed. What you're supposed to do is close the fuel and motor the engine and start over. What's been done is reaching up and flipping the ignitor switch on or to the other system and boom.
I once did a manual start on a 727 where they were slow getting the fire lit. It shot a pretty impressive flame out the back with me and another guy standing next to it on a lift truck. It was dark too so it was even more impressive. Good times.
EDIT: I see neverfly beat me to it. That's what I get for being wordy.