peugeot 306 xsi fuel system

The message from "sarahhewis" contains these words:

It's normal. Don't worry about it. DON'T drill a hole in the fuel cap, they're supposed to be sealed.

I had several Corsas which made the most amazing whooshing sound as the cap was removed. The tanks are kept below atmospheric pressure to reduce escape of unburnt fuel vapour - if they were at normal pressure then as the day warmed up they'd pressurise and then the car would have to have systems to deal with this.

Get your mechanic to buy you a new cap, then DO NOT let him anywhere near your car again.

Chris

Agreed. Sack your "mechanic", he obviously has no idea what he is on.

Its the opposite actually, the tank pressurises until the vapours can be released into the intake and burn off without effecting AFR (i.e. at higher revs) so city drivers will experience highly pressurised tanks, those who spend a lot of time at >2.5-3K revs will not.

The message from "Coyoteboy" contains these words:

Possibly, but I'm absolutely sure the Corsa was a low pressure. You could see the loose sticker under the flap suck towards the inlet sometimes.

It may be that different manufacturers have adopted different approaches to this.

Whatever the case, the OP shouldn't have been drilling holes in her fuel cap!

Interesting, not sure why it would be allowed to go to low pressure, a) itd restrict the pump and b) theres no need as you could add a simple check valve so as to let air in but not vapours out.I'll look into it, if i get time, out of curiosity.

great if you find anything intresting let me no thanks

let me no what u find if its anything intresting

will do thats proberbly why he is so cheap