Overfilled the Fuel Tank - caused lumpy running?

[John Mac]

Glorious sunny day, decided to go for a run, overfilled the fuel tank right up to the filler cap top! after 15 or so miles lumpy running sets in which has never happened before and this continues for about another 15 miles until I get home where it seems to be improving.
Page 68 of the Bible shows a pipe half way up the tank filler neck passing through a "Roll over valve"and going where?
This pipe if it goes to the engine doesn't go through the Fuel filter and I am wondering if its possible to have picked up dirty fuel via this pipe?
Was I burning up the fuel in the filler neck first?
Can't see the pipe as its all behind the wheel arch.
Anyone have any thoughts on this?

[WildfireS3]

I tend to fill all the way up the pipe most times, no problems here.

Someone tell me if it is bad.

[Roy_S2]

WildfireS3 said:

I tend to fill all the way up the pipe most times, no problems here. Someone tell me if it is bad.

Me too!

Roy.

[RichardR]

When I borrowed my boss's S3C many years ago, I filled it right up and soon after parked up with the driver's side wheels up on the kerb, only to find petrol pissing out all over the ground (from behind the rear wheel on the passenger side IIRC)!

I've never seen this behaviour with my S, so it might have been some sort of blockage etc. with that particular car I guess. I didn't really investigate at the time, just moved the car.

[Podie]

Never been one to fill it to the top... but during the summer saw someone fill it to the top... after which it overflowed... so never fancied that myself..

[John Mac]

I did notice a puddle/overfill from behind the wheel when I left the Forecourt as Richard mentioned but still can't fathom out the layout shown in the Bible ( p 68 bottom illustration).
What is this pipe shown and what is a "Roll over Valve" ?

[s1.5f]

Would a "Roll over valve" just be a one-way flap that restricts the amount of fuel that can p$ss out if you flip over? I've seen them on other cars. the pipe could just be the overflow or breather pipe. If it was the return pipe from the injection system I suspect it would always blow rather than suck as the whole system is pressurised.

[shpub]

The roll over valave is normally in the breather or enegine supply and stops fuel pouring out when/if the car is flipped over. Overfilling can only cause problems if the excess fuel has somehow blocked the breather but that is unlikley to happen. More like a dose of crappy fuel.

[TVRDAVE]

If I have this happen to me in Canada the first thing I do is put a Top Grade Gas line Antifreeze in the tank. Anytime of year. It is great for picking up any water that is in the gas and burning it out. If it carry's on like that Injector cleaner. I also don’t buy Gas from that station anymore.


Dave

[swindorski46]

Always filled mine right up and never had any problems.

It did occasionally run lumpy if it'd been left for a couple of weeks, but I just put that down to "Old" fuel. It soon went and all was normal.

[John Mac]

Thanks chaps for all the comments, it seems to be running a lot better so I believe it may have been dirty or water contaminated fuel.
The tick over though seems to have deteriorated so tomorrow I'm stripping off the "idle speed control valve" as I understand this can get gummed up. I will keep you all posted if things improve.