Scirocco Register

Hope this isn't too stupid a question, here goes -
Should there be vapour pressure when you open the fuel filler cap after the engines run up to temperature? I don't want to be searching for a solution if there isn't a problem. MK1 injection.
MOT getting nearer?
Cheers
Andy.

Normal for some pressure in the tank when taking the filler cap off in an fuel injection car.

As Mark said normal, I get it in my Mk2. Don’t get me wrong it’s not like a huge amount but there is some


Jack
South East

www.motorsportdiscounts.co.uk
Seat Leon 1.8T 20V - Track Car
VW Scirocco Scala 1.8 Inj - Toy
Ford Transit 2.0 - Work Horse

Thanks for that gents!
Andy.

how does it pressurize? a vacuum i can understand as the fuel level drops and air cant get in from a blocked breather.

james butler wrote:how does it pressurize? a vacuum i can understand as the fuel level drops and air cant get in from a blocked breather.

To be honest I’ve barely taken any notice of it, it might well be vacuum pressure. I only here it when I’m listening for it lol


Jack
South East

www.motorsportdiscounts.co.uk
Seat Leon 1.8T 20V - Track Car
VW Scirocco Scala 1.8 Inj - Toy
Ford Transit 2.0 - Work Horse

If you don't have the ventilated fuel filler cap, then the tank vents to atmosphere via a gravity valve up inside the arch near the filler neck. from there it goes down to a long thin tube on the tank which might be blocked.

There should not be much pressure in the tank at all, that could be dangerous

Ill get it up on a ramp tomorrow and check the pipes in r/o/s arch - and it may well be a vacuum? but there is a definite difference in pressure to atmospheric - positive or negative

It's normal - there's a very good k-jet guide on the Mk1 Golf Forum:

15.1.2 The Fuel Tank
The fuel tank is the obvious place to start in any fuel system explanation - unlike the tanks on early carburetor fuelled engines it is a sealed unit. This allows the natural gassing of the fuel to aid delivery to the pump by slightly pressurising the tank It may be noted that when the filler cap is removed, pressure is heard to escape. Filler caps are no longer vented as previously found.

https://vwgolfmk1.org.uk/forum/index.ph ... ade-easy_2

It's not noticeable on my Scala, but very noticeable on my previous GTX.

'slightly pressurising the tank'

Thanks all :)

Thanks very much for the link - will also help with the high tick over of 1500rpm! Some very good info.
Cheers
Andy.

blakey wrote:It's normal - there's a very good k-jet guide on the Mk1 Golf Forum:

15.1.2 The Fuel Tank
The fuel tank is the obvious place to start in any fuel system explanation - unlike the tanks on early carburetor fuelled engines it is a sealed unit. This allows the natural gassing of the fuel to aid delivery to the pump by slightly pressurising the tank It may be noted that when the filler cap is removed, pressure is heard to escape. Filler caps are no longer vented as previously found.

https://vwgolfmk1.org.uk/forum/index.ph ... ade-easy_2

It's not noticeable on my Scala, but very noticeable on my previous GTX.

Noticed this on mine when i got home from work the other day. I had perviously noticed a petrol smell from the rear the other day so i assume it has a leak of some sorts, the opposite side to the filler neck the tank looks damp ish but not dripping. Then friday after a drive home from work it was hissing from the same area. Took the cap off and the pressure behind it was quite substanial. Dont ever remember it being that bad. I've parked it up for now and using my daily again. Something to add to the list and investigate in due course!!