Technical Barchetta Fuel Cap -fuel smell

[Simon440]

On various mediums I have seen the fuel cap listed as a cause of the fuel smell in the B's.
People have reported changing the fuel cap and the smell no longer being a problem.
My question is why would this be the case?
If the seal on the cap has failed surely this would negate the fuel tank pressurising ( which I understand, is what causes the vapors to escape by pushing them through the old seals)
Am I missing something?
How do you check your cap, mine looks ok and the is certainly allowing the tank to pressurise.

 

[wapper]

There's a lot of topics here about fuel leak and smell, a fairly common problem. The reason is usually in the connection between filler hose and the tank.
I don't think the cap is to blame here, but it if was, it could be detected easily with your bare nose.

barchetta fuel leak | FIAT Barchetta

So on to the next issue....; fuel stank. Questions: 1) When the tank is full and without any tank pressure build-up, there is a leak around No. 14 (see pic), part No. 46755835. Do you have any suggestions for a solution, eg is there any sense in trying to apply a liquid seal (it needs to hold...

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Umfassende Informationsseite über die von 1995-2005 gebaute Fiat barchetta (Typ 183).

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[Simon440]

I am planning to look at the seals and hoses as others have written about, just curious as the fuel cap gets mentioned and has been identified as the cause by some.
Just out of interest does anyone know how pressurised the fuel tank should get, mine release quite a bit of pressure when opening the fuel cap, particularly in warm weather?

 

[wapper]

Mine also does quite a loud hiss when cap is opened. Which way the hiss goes, in or out, I'm not really sure. I think there's a bit of a vacuum in the tank, because of the fuel vapor removal working.