Gas tank vent
The vent from the tank is vented to the atmosphere and the vent tube from
the fill tube goes thru the rubber seal sealing the fill tube to the body.
Some one posted the other day on a similar question that they put a fuel filter
on the tank vent to keep out critters. I'll have to give that a try.
Here's the other thread:
http://www.forabodiesonly.com/mopar/showthread.php?t=96894