I had a gas smell like yours and it was the washers on the banjo fittings of the fuel pump. You have to crawl under the car, right rear near the fuel tank, and look for wetness around the fuel pump and filter fittings. It doesn't take much of a seep to smell strong. I went to NAPA and they had some alum washers close enough to the right size for less than a dollar.

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85 300 SD ~ 115K
82 500 SEC Euro ??K
78 450SL 164K