I'm thinking maybe something to do with the exhaust, from the pop sound.
Usually 02's are rusted in practically though.  but that's a good and easy
thing to check.

And the clogged cat or muffler is a really good thought too.  If it was bad
enough it could keep an engine from starting.
And the white smoke ? 
Scott 

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Geza Polony
Sent: Saturday, December 29, 2007 6:36 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: My '86 "Blue Mongrel" - R.I.P.??

One question I'd ask is whether a head gasket failure typically begins with
a sudden Pop sound. If not, then maybe there's something else wrong with the
engine. I don't know the answer to this one, but before assuming the worst,
it's worth making sure the engine is really kaput.

I once had an 02 sensor pop out and that definitely makes the van sound like
an ancient lawn tractor. Could her problem be something with the exhaust,
maybe a sudden failure of the cat or muffler baffles? That might explain the
loss of power, maybe not failure to start, though.