My 2008 Audi A3 2.0 Tdi BMN engine - mileage 150k, has had been a bad cold starter for about 2.5 years. It cranks but does not fire up. It is intermittent and random, then sometimes it starts spot on ! Drives very well, but to add to the mix I notice .... very very occasionally and randomly, I feel there is this very very slight hesitantancy ! April 2017 - I was getting juddering (kangaroo hops) at very slow speed in traffic and bad starting. So I had the tandem fuel pump and tank sender unit replaced as advised. All coolant hoses were replaced due to contamination due to the leak. Then the tandem pump failed again in November a few months later and was replaced under warranty. April 2018 - Bad cold starting / juddering was still happening, the dealership did tests and advised that it was a injector problem. Replaced all the injectors and associated parts, plus the oil cooler and turbo booster hose. January 2019 - However, the problem still was still there. Back into the dealership it went, only to be told that the head was leaking and it needed replacing ! I did not see any of the usual evidence of the head failure, so it didn’t get done. During the course of 2019 and early 2020 there were several visits to the dealership for this problem. They tried a new starter motor, but that wasn’t the problem, and the part was returned. The only thing that came up on the diagnostics was the engine speed sensor, but as it was not definitive enough I did not replace it, as I felt it was becoming a bit of a guessing game. Being told the head was porous kept coming up. Again not definitive enough at £7-8k, that was not going to happen ! 2020 - Around January / February I have another diagnostics done, but that did not really reveal much other than the ignition key halo might be the problem, but again not totally convinced so I did not do that. Early March I had it booked in another garage following another starting episode. It was determined and I was shown that the starter motor connection had been damaged by over tightening, possibly when I had the gearbox and clutch done in late 2018. This was causing a drain on the battery especially after 5-6 cranks. So starter motor and battery (2 years old and the smaller capacity) was replaced. Leak tests on the fuel system tested, no leaks found. So next the timing was in line for checking. As the cam belt was due for replacement I had it replaced at that time. No issues with timing found. Then disaster struck, the tension stud failed and The belt slipped. The engine incurred a hole in the block. Replacement remanufactured engine fitted. Injector harness replaced, along with engine speed sensor and new turbo. Unfortunately the problem is still there. Again leak tests and fuel pumps tests carried out, all good. Replaced tandem pump made by Bosch, showing better pressure. Test driven and runs lovely, smoother pickup. Just waiting to find out if the starting issue has gone away. The next course of action possibly the fuel pump (with regulator)that feed the tandem pump or the ECU. Any ideas what is causing this very very frustrating problem please ???