The cap on the fuel tank fill is very tight and need strong pressure to remove. The gasket that makes contact with the filler neck is wet even though the tank is almost empty. I don't recall the cap being hard to remove or the gasket being wet, am I mistaken? Thanks for you opinions and advice.
The vehicle is a1983 240D.
Anthony

my filler neck gasket is never wet unless I drip during filling. sounds strange to me

Sounds like your tank vent is plugged. It should need a lot of effort to take the cap off. Climb under the car and near one rear wheel or the other you should find a little bell shaped rubber piece on the end of a metal line. That is the fuel tank vent. Make sure the bell is clean on the bottom.

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