Hi Folks 👋, first time posting for me so thanks to anyone who can share any opinions they might have with what might be a large repair bill. It's at the garage so I'm not trying to repair myself but interested and dreading what it might be.

I have a 2016 A3 sline 1.6 tdi. It's done 85k and had a stage 1 remap done approx 35k ago, since ran on premium diesel with no issues other than more frequent regen. It's regularly serviced and not really driven in dynamic too often.

So broke down on the motorway, no dash warning lights other than message saying 'turn car off and restart' the car would turn over but no catch. The AA got it to start but only by spraying into air intake but it stopped when he stopped. The garage I was towed to is saying all the fuel is being returned to the tank. I was hoping that the issue was with the tank pump but dreading it's the upfront high pressure parts.

And that's all I know at this point, a bit concerned really. Thanks for any opinions 👍

Difficult to say without scanning with VCDS. If it is fuel starvation, either the fuel pump in the tank, or the high-pressure fuel pump. If it puts your mind at rest look at Audi OE parts via LLL Parts so you potentially know what you're dealing with. Do you know when fuel filter was last changed? Should be every 20k miles. Not suggesting it's that, but something else to consider.