I have a problem where my mechanic is telling me gas is coming through 1 of the vacuum lines that goes vacuum canister.... I think that's what it is called, it sit's behind the passenger headlight... Anyone ever seen this?

 

There are several vacuum check valves there along with several vacuum hoses. And I've seen liquid fuel accumulate behind one of the vacuum check valves- enough you could dribble fuel out of it.

The design of it generally prevents liquid fuel from being drawn into the engine via the purge hose (or the vacuum actuation hose) no matter how screwed up things get, however. First off, it is nearly impossible for anything but fuel VAPOR to escape the tank via the vent lines (that go from the tank to the charcoal canister). Secondly, if they do, the only way liquid fuel can get from the canister to the engine is if the diaphragm in one or more of the vacuum check valves ruptures and and directly connects things that were never designed to be connected directly to eachother.

Although I have never taken the time to prove it, I think the possibility of sucking in any serious quantity of fuel- liquid or vapor- through the charcoal canister system is HIGHLY exaggerated. The minute vacuum is applied to ANY of those hoses or valves, even if they have liquid fuel in them, it would be consumed very quickly by the engine. Looking at that system as a source of an ONGOING (over-rich) problem seems unlikely to be the right diagnosis.

And also remember that the system, even if working perfectly, is DESIGNED to purge fuel vapors from the canister under certain conditions anyway (engine warm, above idle). So fuel vapors getting into the engine via this system is SUPPOSED to happen, under the right conditions.