2002 Fuel line or ventilation ??

I finally got around to changing my fuel filter and found the hose just above it leaking. This line has a connector just like one end of fuel filter and goes up toward front of engine, but what is it ??:confused: My service engine light came on last week and I'm guessing this may be the reason ??? Also it only leaks when the car is running... :banghead:

Rob

Sounds like the vapor line or the fuel return line, most likely return if fuel comes out.