Ditto to what Benzmac said. Also, although I'm not 100% sure if your car is the same as my 126, but there is a hose inside the tank flap, next to the fuel cap. On my 1983 300SD, this hose goes through the trunk and out under the rear axle area (roughly). If this hose comes off, like mine did, overflow from the fuel tank can get directly into the trunk area between the fuel door and the trunk hinges. I was able to push mine back on, but I had to climb in the trunk after removing the trim panel.
Lehigh Valley PA USA
73 Olds 88, 72 MB 280SE, 78 Datsun 280Z, 71 T-Bird, 72 Olds 88, 83 Nissan Sentra, 85 Sentra, 73 230.6, 91 Integra, 83 300SD, 91 Volvo 940GLE wagon, 84 300SD, 95 Subaru Legacy L wagon, 02 Mountaineer, 91 300TE, 08 Murano, 2007 R320CDI 4Matic 52K, some Hyundai, 2008 BMW 535xi wagon all gone... currently
2007 Honda Odyssey Touring, 2011 Honda Odyssey Touring