Issues starting - but not with race fuel

[gbleenz]

For 6 months or so now, when I turn the engine over it will run for a few seconds and then cut out, regardless of engine temperature. More often than not, it will keep running after starting it for the second time. On occasion however, it has insisted on being started three times before it will keep running.

Last week, I ran the tank right down to empty and then filled it with 100 octane fuel prior to a day at the track (which I didn't end up going on). I would usually fill it with 95 or 98. I haven't had any issues starting the car whatsoever since filling it with race fuel

Could this simply be coincidental? Or perhaps an indicator of what is going on? I've had a hunt around on the forum, but couldn't see anything specific to this problem. Perhaps I should just keep using race gas :mischeif:

Any advice would be much appreciated

[Thuppu]

Is your fuel pump check valve ok? If the fuel drains back to the tank when the car stands for some time..? Don't know how the fuel could effect this though?

[gbleenz]

Is your fuel pump check valve ok? If the fuel drains back to the tank when the car stands for some time..? Don't know how the fuel could effect this though?

Thanks for the suggestion. I'll have a chance to check it out early next week.

Any other suggestions for things to check are still most welcome

[gbleenz]

Turns out that the issue was with the ignition switch.

Had my local Audi workshop look at the car & they found that the faulty switch was causing the intermittent problem.