I have seen many discussions on the problem of TDI engines being hard starting after say 12 hours , i found on another forum that the injectors need a back pressure of 10 psi to work , normally this is held by a valve after engine stop , but this valve can leak slowly lowering the retern rail pressure so car will start all day every day once the initial startup done ,
My car a 2007 TDI started with this problem it would take 20m seconds and numerous trys to start it , then once started stopped and started no issues , the fix is very easy and not any fix that Audi will tell you as they prefer the change all the parts method , here is the actual solution that fixes the problem :

let fuel tank fall to 1/4 full , add two bottles of a good diesel injector and fuel system cleaner to tank and drive until the tank is almost empty then fill with regular diesel , you will find after one day of driving with this cleaner at high concentration hard starting is gone : Reason ? the valve that closes and maintains the fuel return rail pressure gets clogged and gummed up allowing the pressure to leak out , takes many hours but it does then fuel pump has to build the pressure back up to min 10 psi for injectors to work ( on the return side ), to stop it happening again add a bottle of cleaner every 3 tanks , cost to fix few bucks and no parts changing from your friendly dealer oh what a shame , read some of the forums on this problem you will be shocked at what Audi changed on the parts for some customers only to find out it did not fix the problem , happy motoring

 

I bet there is a mvb to check the rail pressure on VCDS. I would check it during the cold start and then during a hot start and see if there is a difference. I always recommend adding a good Cetane booster every few tank fill up. Especially during these cold winter months. And if you really want to keep those rails/fuel systems clean, add a can of Diesel Purge with every Fuel Filter replacement. I offer that with every fuel filter service at my shop.

 

Hi Thermotec2010, where are you from? I tried that but it didnt work!