Fuel -breathing system issue?

[piotr]

Hi.I always he'd little smell of fuel around my car but no leaks.Tough it's the aftermarket fuel cup not being good enough.I have bought brand new OEM cup thinking this will sort the problem out.Today I have done long trip and when I opened the window still driving I noticed strong smell of fuel .Again,no external leaks.When I opened fuel cup the exhaust fumes have been strongly pressurised in the tank .It looks like there is a problems with tank breathing system and I'm not sure what to check now
im just thinking when I was replacing all fuel lines,is it possible that I have mixed up breathing and fuel return pipes Also I could hear from the tank sound like water dripping in to the bath.It would be handy if someone he'd diagram of fuel system/breathing system so I could make sure that I didn't mixed up any pipes but I don't think it's possible

[Error404]

I have the same issue with my car mate. I have deleted the breather circuit in the engine bay and my tank breather goes to a small filter behind the rear bumper. In theory the tank just vents to atmosphere, but yet I still get a build up of pressure in the tank, and i think this blows past the seal on the top of the tank or leaks out of the breather tubing around the expansion tank allowing fumes inside the car. I am pretty sure the cause is the roll-over or check valve in the breather line coming off the tank - either or both are blocked preventing the breather circuit from working adequately. I have a new roll-over valve, tank cap seal and check valve to fit and I plan to replace all of the rubber hoses that make up the breather circuit at the tank end too.

HTH

[piotr]

I'm glad I'm not the only one with this problem
and yes,I forgot to mention that I noticed slight smell of fuel in the boot as well so it looks like it is blowing past the seal on the top of the tank.could you give me part number for them two valves please buddy,I will replace them as well .

[A80Avant]

I recently had this issue as well. 2 things I ended up doing was replacing the tank cap that connects to the pump as it had hairline cracks and also deactivate the charcoal canister. Fuel smell has gone. However I will reconnect the canister again.to see what happens, as currently I don get my tank to pressurise but reading the above I wonder if this will eventually damage the check valves and give me this problem later on

[piotr]

I need to get to the bottom of that ,find the problem and fix it without any modification.its been designed and should just work.hope it's something silly as one of them little valves.
where is it actually releasing the fumes,is it the little pipe on the right hand seal?

[SteveH]

I've deleted the carbon canister on my motor and I always get a buildup of pressure in the tank. It's been like this for the past 15 years, so I'm assuming it causes no real issues.

[GazzaG60]

you may find the original system helps pull the vapour from the tank helping depressurise.

when i removed mine on the s2 i didn't have a smell of fuel. ensure the seal on top of the tank is in good if you have had the pump out. without the metal tank cover on you can see issues. with it on they are hidden.

try running with a loose cap and see if it goes away.

think the pressure buildup is more an issue on gravity fed tanks like my b3.

[SteveH]

Mine was the same before and after the carbon canister delete. I've never changed the fuel cap, so that could be the culprit.

[newsh]

I used to get a honking sound when the tank was low, this continued after the carbon can delete. There's a check valve in line from the breather tank just below the filler cap to the carbon can, all my pressure problems disappeared when I deleted this valve.

[piotr]

I will have a look in to it right after my holiday as it's taking all the pleasure of driving it when you can smell that fuel.

[piotr]

Thank you John

[newsh]

Thank you John

Also
Have a look in my thread for the fuel tank repair lots of have had to do, where the small pipe drains back in from the breather tank, it can be repaired with chemical metal.

[Bowie69]

I had the same problem, and the same fix, still going strong 3+ years later

[piotr]

Cheers boys