Hi,
   I noticed your problem with the fuel odor and loss.  I used to have
the same problem and I thought you might be interested in how I fixed
it.   Everytime I filled the tank full, I would loose about a half a
gallon of fuel and it seemed to be coming from the top of the tank.  Now
Vanagons are known for the tops of the tanks rusting out and thought
this was my problem.  One day while I had the wheels off the front I
stuck a mirror in the wheelwell to look at the top of the tank.  TO make
a long story short, there are 3 rubber gomments on the top of the tank
that hold plastic hoses in place for the vents.  It turns out that
someone removed the tank, either to replace it or fix the fuel level
sending unit.  Whatever it was, when they put the tank back in they
pulled on one of the hoses and it pulled the grommet loose sightly. 
When I looked at it appeared to be in place but I could see signs that
it was leakin.  Perhaps it that might be your problem.  The gromment may
be loose or worn out.  In either case you can replace then without
removeing the tank.  You can reach them through the wheelwell.  I
removed my tank to fix the hose the was pulling on the groment in the
first place.  My tank, luckly was replaced and looking as good as new. 
Goodluck.  Take care.
-- 
                            -Jim Digennaro
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