I have the smell of fuel in the passenger compartment and my trunk in my 85 380SE.

Suggestions on what to do to fix the problem?

Brian

Assuming it is not a fuel leak anywhere, I would check the fuel tank vent valve. When functioning correctly, it is supposed to release fuel under the rear pax foot well in over-pressure conditions, but if malfunctioning it could release fuel under normal pressure.

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Don't Chrome them; polish them

First off confirm that you do not have a fuel leak, if you do I would not recommend driving it at all.

Inside the fuel filler door, check that the gasket that surrounds the fuel filler neck is in place and in good shape. If it isn't an overfill can get fuel down the outside of the filler neck into places it shouldn't go e.g., the trunk.

Also check that the fuel cap is in good shape and installed correctly.

Check that the drain hole in the fuel filler door area isn't blocked and that any liquid (test it with water) exits outside the car.

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

This problem doesnt occur when the tank has just been filled, so, thinking its not related to fuel spilling inside the fuel filler door when I fill the tank.,..also, no evidence of a fuel leak anywhere.

I do have quite a bit of pressure when I remove the fuel tank cap,...is this correct, or does it indicate that something is blocked?

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

where does the vent valve live,.....and how is it checked?