> After letting the van sit overnight with the main valve off,
> I cracked open a stove burner valve and heard a hiss of gas
> for a moment.

Did you do this before last night?  If you turn off the stove, then turn off
the valve at the tank, there's some gas trapped in the system.  Try it again
tomorrow morning before condemning the main valve... 2 failures (the valve
leaking into the system, and then something in the system leaking too) would
be too unlucky :o)

toodle pip,
--
       Dug Smith         | Homer Simpson:
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