Check your gas cap seal. if thats what it is, it's only a few bucks for a new cap. Very interesting that you bring that up,,, I forgot to put my gas cap back on today and lost about a quarter tank shooting out my filler nozzle,,,OOPS!
Good Luck!
Adam

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Current Stable:
01 ML55 AMG
92 500E (a few mods)
87 300E (lots of mods)
00 Chevy 3500HD Diesel Box Truck
68 18' Donzi Marine
06 GT i-Drive7 1.0 Mountain Bike (with GPS!)

PREVIOUSLY OWNED:83 300SD, 87 420SEL, 88 420SEL, 90 420SEL, 86 560SEL, 86 190E 2.3-16V AMG, 94 E320