I'm an idiot sometimes. For some reason I thought you were talking about the injector o-rings. That explains why you couldn't pin-point the problem to under the hood or near the tank...

I think you may be on to something with the connections at the ends of the fuel lines, but I'm wary of it because those connections seem pretty foolproof.

I'll ask obvious things: You park in a garage at night, ie enclosed area where you're more likely to smell fuel (explaining the odd timing of the smell)? Filler tube or filler tube connection to the tank?

This is a longshot, but has your car had the recall fix for the fuel tank? Apparently the tank could crack due to the mounting points or something. I got a letter from Volvo and took it in so they could inspect the tank and add some rubber bushings to the tank mountings or some such thing. This was around 2.5 years ago. This was only applicable to certain states with colder weather. Let me know and I'll pull the letter/dealer invoice from my file.

--Will
850 / Mini
--
850 / Mini