filler neck modification

Brad4406 said

I've been watching this thread for a while, but IMHO I don't believe the true cause of this issue has been identified. I don't see how a flapper valve has any ability to prevent this issue.

It's been a few years since I've owned anything but an early A, but don't the later As have a gas tank vent tube that connects towards the top of the filler neck? Any chance the lack of this on the early As is causing the issue?

I have my early A filler neck out of the vehicle, so I can post some pictures for the end that goes inside the gas tank. Maybe a later A owner can post a photo of theirs in that area so we can see the difference.

I plan to test this theory by tapping my filler neck and running a vent tube down to my fuel cell, but I'm a long way from being ready for accomplishing this.

Click to expand...

I use the filler neck mod. (but my early A has a vent near the top it look to be from the factory) As a kid (a long time ago) I worked on service station pumps and they used to be pressure activated shut offs. (there was a small tube in the gas nozzle that would detect the back pressure of the gas as it filled up). Sometimes we had to replace and calibrate the venturi to make them work. later on they just started replacing the nozzle(easier). using the flap mod it makes the air flow past the gas nozzle a little faster causing greater back pressure and that's what kicks the nozzle off,if it's installed right by being sealed good to the tube so air flows only through the hole or you just slice the tube and weld in a washer that has a hole just big enough to let the nozzle in. if you have no back pressure then no kick off of the nozzle. but it'd help if the tube was angled slightly different like the later A's are, that long slope just sucks! AND it doesn't do anything for driving and turning spills. only a good cap or different filler tube design will help there.