Citroen Xsara Picasso fuel smell

could be a faulty charcoal cannister under the bonnet.

Could also check the obvious i.e fuel cap seal .

Not sure what it does, some kind of vent or return, but if you remove arch from under the petrol cap ( will need to take the wheel off) you can access the black plastic part of where you fill with fuel (sure there is a technical term;just don't know what it is). On it, there is a cheap plastic connection which is prone to snapping, which then vents the smell of fuel when you are driving. This also explains why you are not losing any fuel when you park or run the engine. I had the smell for about 5 months, every time we opened the window or turned on the aircon you could smell it. I think the part costs around £80 but we just did a bodge repair to solve it at the time.

hello , just to let you know guys but if you have a xsara picasso smell petrol when driving with window open it s very likely to be the connection behind you fuel filling cap:
it's very easy to check and only take 5 minutes remove the five screw where to fuel cap is and you will need to remove the fuel cap too be this will let you see behind and you will be able to see if one of the pipe as snap which is very common on this as Mark 30 said .
you probably wonder how can you smell the petrol this when your window are open/

well when you driving this create a draft and the smell actually come from your boots and then is push back toward the window to excape.the fuel fume come up the the wheel arch and suck in by this draft .
but if you have the window close and you only use the fan well you can not smell the fuel because by doing this you bushing the air in the back of the car to escape .

I hope this can help because I have spend many day s to tried to figure out the smell and a lots F*** swearing .
so if this are the symptom on you car please check this basic because it took me a while to figure this one out .