Spotted above, need to read a little more

Sorry! I was too hasty - trying to get away from the lights too quickly! So, would you recommend me taking it in to get checked? I think this could be a design flaw if it is so easy to do.

My reasoning is like this. When I fill up normally, there should be pressure in this vent volume keeping fuel out. When I replace the filler cap, this volume is vented, so it (partly) fills with fuel. This fuel comes from the main volume of the tank. There is room to put more in - maybe not the full 7 litres, but some of it.

Nah, not really, the expansion tank is higher than the fuel tank so very little fuel will reach it only maybe what is in the "brimmed" pipe between the tank and the filler mouth but not much really.

Fuel Tank

The extra capacity is not meant to be filled. It houses vapour ready to be recycled. No fuel enters it when the nipple is pressed down by the car, just any vapour/pressure in the tank.

The tank has to be vented to atmostphere or it would just fold in when the fuel pump ran. But you cant just have a vent pipe running off the top of the tank.

Nah, not really, the expansion tank is higher than the fuel tank so very little fuel will reach it only maybe what is in the "brimmed" pipe between the tank and the filler mouth but not much really.

Fuel Tank

Thanks for the picture. It looks like the expansion tank is the triangular component on the vent pipe. As you say, probably not enough in the filler pipe to fill it up.

Just noticed that you're an Airbus engineer, at least you don't have to bother with MTOW on the Fabia & just as well by the sound of it !

The extra capacity is not meant to be filled. It houses vapour ready to be recycled. No fuel enters it when the nipple is pressed down by the car, just any vapour/pressure in the tank.

Yes, because there is not enough fuel in the tank and pipes to fill it. But if you are refuelling and accidentally press it down with the nozzle, it could be filled. So, on the picture that TD-eye posted, where are the components (solenoid, filiter) that could be damaged by an overfill?

Yes, because there is not enough fuel in the tank and pipes to fill it. But if you are refuelling and accidentally press it down with the nozzle, it could be filled. So, on the picture that TD-eye posted, where are the components (solenoid, filiter) that could be damaged by an overfill?

23 is the filter, not sure about the solenoid (mine's a diesel & doesn't have these bits) & yes the expansion tank is the triangular bit.

Just noticed that you're an Airbus engineer, at least you don't have to bother with MTOW on the Fabia & just as well by the sound of it !

Yes. I work on the analysis of wing strength. The only passing acquaintance I have had with refuelling was many years ago working on Concorde. In the hangar, one was filled up with the tanks in the wrong order - rear first - and it sat back on its ar5e. Not done that with the Fabia - yet!

The solenoid isn't on that picture, its under the bonnet.

If you brimmed it by venting the nipple at the filler neck either deliberately or by accident you would get approximately an extra 7 litres in your tank.

I have now filled up again - a typical 38 litres and not quite on the reserve tank. So last filling of 50 and this filling makes a total of 88 litres. The mileages were 287 and 412, making 26.1 and 49.3 mpg. These average out at 36.1 mpg, which is reasonable. The type of driving was similar.

If I assume average mpg, it does mean that 51.9 litres was used from one filling. I was only about 3 miles into the reserve tank. This would suggest that there is more than 7 litres capacity in the vent tank and associated pipework - up to nearly twice as much. Unless my reserve tank is grossly over-reading. This would be unlikely as I have been halfway into it on occasion.

. This would suggest that there is more than 7 litres capacity in the vent tank and associated pipework - up to nearly twice as much. Unless my reserve tank is grossly over-reading. This would be unlikely as I have been halfway into it on occasion.

Mike I suspect that you might be right there !:eek:

Looking back over fuel receipts for SWMBO's Fabia I'm regularly seeing receipts for between 50 & 53 litres of diesel post ventectomy suggesting that indeed the expansion tank holds more than seven litres. (SWMBO generally refuels either just before the fuel warning light or just when it comes on.)

Witness this thread I posted a wee while back for instance:

http://www.briskoda.net/forums/fabia/m-p-g-calculator/80877/#post927666

I think the figure of seven litres originally came from my findings after the first refill following doing my first ventectomy on my own TDI Golf. I may have just assumed that the Fabia would be about the same capacity but it seems perhaps not now, it may have an even larger capacity in the expansion tank !

I topped up at a BP station again today. On the nozzle, there was a proud ring about 80mm from the end. When I put the nozzle in the fuel tank neck, I could easily arrange for this ring to trip the lever to the vent tank. If I were to have filled it in this position, I would have filled the vent tank. Possible damage could have resulted, so I have heard.

The next time you refuel, have a close look at the nozzle and this lever. See if you can toggle it as easily as I could. I think the design could be improved here.

I have attached the picture of the neck of my fuel taken showing this lever.