I replaced my fuel tank a few weeks back.  The cross over pipe was difficult
to put into place... It would not fit into the drivers side of the fuel tank,
so I pulled and pulled and it still would not fit into the grommet, the pipe
seemed too short, well it turned out that I had the crossover pipe on
backwards... I just bent the tab that holds it onto the body down and then it
fit perfectly... Well, I was smelling fuel after I filled up and thought that
I had damaged the pipe because I had pulled on it so hard to try to get it
into place.  Well, I pulled it out and replaced it with a new pipe and new
grommets.  This should fix it I thought ... well after I was done, I stilled
smelled gas.  I then looked and knew it could not be the NEW part I just put
on...  Could it be the NEW fuel sender or NEW gasket or even the NEW fuel
tank that was leaking?
I then decided to pull the expansion tanks off and check to see if the gasket
was leaking...  I pulled (pried) the tank off and on the drivers side and was
met with a shower of dirt and rocks.  The gasket had split apart and dirt had
gotten into the tank due to the poor shape the gasket was in.  The vent/check
valve was clogged and would not move.  It was stuck closed due to dirt and
the gooey tar-like (the rubber grommet had turned to this) substance.  I
cleaned out the vent/valve and put it back.  I did the same to the passenger
side, it was just as bad.
NOW NO MORE GAS SMELL! :)

IF you are changing the seals out on your tank due to leaking fuel vapor, do
not over look these grommets.

The van evens seems to run stronger since I changed these grommets out and
cleared the vents to the expansion tanks.

Robert