Van starts, runs fine but when shut off it will only turn over, will not start again

What is your question?

Used to be sporadic not firing up problem and I was having to "bump" the key/starter a few times to get the van to start up. Now, the "bumping" doesn't work. Neighbor says he had a similar problem with his Grand Voyager that turned out to be an emergency fuel shut off switch, but I can't find one of these on my van. Any ideas of what to check for the problem and/or where to find the shut off switch?