'90 300SE fuel smell under hood

[86560SEL]

A co-worker has a '90 300SE with the same engine as my '88 300SEL and had asked me this, but I have no clue. He said the other day he faintly smelled gas and smelled between the crack of the fender/hood and could smell some gas fumes... not bad though. He said its been like this for awhile, but there are no fuel leaks to be seen visibly and the car gets about 21 mpg. I did a search and seen where some people with 300E models mention something of a EHA valve that sometimes leak on these cars, but I looked and it looks like a relay of some sort to me? Looks quite costly as well. His mechanic told him that it looks like the way these engines are designed that a fire from a fuel leak is low, because the exhaust manifold is on the passenger side of the car and there is nothing on the left side of the engine that really would get hot enough to spark a blaze, but nevertheless, he does not want a fuel leak if something is occuring. The mechanic also said, "of course you smell gas, what do you think this car runs on, coal"? lol. I have yet not to smell a little diesel fumes under the hood of a diesel engine, so I guess some gas fumes on a gasoline engine car (especially older) is not really that uncommon or cause for concerns?

I looked around my M103 engine today and I did not smell raw gas fumes, but if I get close to the air cleaner I can smell some gas fumes (when the engine is fully warmed), but it seems to be coming from the hole in the center of the air cleaner cover... I guess this is normal? I also thought I would smell around mine and after a 40 mile trip, I pulled in the driveway turned the car off and went to the front and smelled in the grill area and faintly smelled gas fumes, but not major and I do not see any fuel leaking on my car either. My old '85 380SE had some sort of a canister by the radiator that always omitted gas fumes. No one knew what it was though.