A friend of mine had his vanagon die in the middle of the highway.  He said
he had a very strong gas smell in the engine compartment.  It turned out that
it had something to do with his injector rail.  Something about something
deteriorating.  Sorry I couldn't be more help, but your problem sounds very
similar to his.  I'm going to talk to him to find out for sure.  

If anyone receives this please e-mail me.  I've posted one message so far,
everytime I try to post another it never shows up.