I believe I remember reading in another post that some people with that fuel smell replaced their filler cap and it solved the problem.
Did you perhaps forget to put the cap on or not put it on correctly?
That might help the problem.
I think if you search for gas smell, you might find the post that had it.
I'm not a tech, just relaying what I have read in another post about gas smells.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.