Hello all. I have a 95 S10 Blazer that I use on my mail route. I start each day with a full tank of gas and lately after a couple hours into the route I have fuel leaking from the backside of the fuel filler neck area inside the fender. When I loosen the cap there is a big whoosh of air coming out of the tank. It's not the 2" filler hose that's leaking so it must be the smaller one immediately above it. Is this a vent line that has become plugged or something? I just figured out that if I don't tighten the cap it does not leak but don't want to do that for long. I'm stumped on this one.

 

if your vehicle has a vent valve it could be stuck closed causing it not to vent. also your charcoal canister can be filled with gas causing a similar situation

 

The filler necks are known to rust ou and get a hole. Mine did. Also my blazer always has a "whoosh" when I open the cap.