Has your fuel tank got a vacuum in it?

[Rikki Kitto]

Any new news on this?

[Toph]

My tank is vented to atmosphere, yet I still have some vacuum (I don't believe it is pressure) in the tank when I remove my cap. I'm not sure why it doesn't stay neutral, and will have to take a closer look at the system coming from the tank. My vent hose terminates near the fuel filter, so if there's a problem it is on the tank side of the system. I know this only adds to the mystery, so sorry for that, but I figured I would share my experience.

[Rikki Kitto]

Thanks anyhoo problem shared is a problem halved n all that

[newsh]

Mine still has vacuum with the carbon can removed and the pipe open to atmos, never got round to looking at the stuff in the boot properly..

[Rikki Kitto]

It's a bit of a mare, end up leaving the cap slightly undone to stop it

[Cottis]

Every coupe I have had has done this. I would be more worried if it stopped.

[Rikki Kitto]

Is it to the point where it starts chucking petrol back out the filler cap when you undo it

[Cottis]

Blimey no. Definitely not. Just a whoosh of air depending on ambient air temps I would say. Mind you, I could count on one hand how often the tank has been brimmed. Is your tank near full when doing this? If it is spitting out fuel, that sounds like more than just a build of pressure. My old CQ's used to do it and they were daily drivers which were brimmed each week and they never spat fuel out at me. I wasted fuel in other ways haha

[mrtat2k9]

problems i have is the valve thats near the tank has gone faulty. i was under the impression this valve lets air back in to the tank has fuel is taken out. and has tank gets hot and fuel and air expands it lets the air out. just my side of things

[newsh]

With my coupe I get a "singing" noise as the tank gets down to the last quarter. When I open the cap at this point it goes "skooosh" quite loudly. Definitely vacuum.

[SteveH]

Mine still has vacuum with the carbon can removed and the pipe open to atmos, never got round to looking at the stuff in the boot properly..

Same here. No carbon canister and one pipe open to atmosphere. Still a distinct rush of air when the cap is removed...

[Colesy]

Maybe this could be the problem!

[newsh]

[Rikki Kitto]

Love the reply from the mazda man