Your leak may be coming from a fuel hose attached to your fuel pump(s), not the tank!
The pump(s) reside under the car just in front of the passenger side rear tire. The assembly is protected by a plastic cover which must be removed first.
Even a pinhole leak in the fuel hose can wreak odorous havoc!
I had to deal with this twice. A loose hose clamp on the SL fuel hose dripped enough to fumigate the interior, while a leaky one on the W124 didn't drip, but it smelled up the garage after a long drive!
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car