TDI hot start issues

[ainarssems]

If the fuel filter was blocked it would let fuel through at lower rate and mostly affect high load situations not so much starting. I think It may well be combination of problems. It could be weak battery combined with poor electrical connection to starter and weak starter itself. The fact that it turns faster and starts when jumping from another car means that battery is weak. 3 new batteries in 2 years does not say much, it could be duff batteries or a fault with a car draining/damaging batteries. Check the battery if you can find a place that does it properly. Portable testers like many Halfords use will only put 100-200A load on battery and is not sufficient for a large battery like in A8. You would need at least 400A load, even better if you can do 800A; which means a lot of heat released which I am not sure if can be achieved in portable unit. Battery testing benches have large resistors and large fans to cool them down to allow high drain for longer period. Conductance testers like this https://www.aliexpress.com/item/Orig...0-2990ba944727 can give you general picture but are not very accurae when it comes to larger batteries. In my expierence anything less than 100% health indicated mean battery is on it's way out.

Where are you located? Some of the forum members might assist with VCDS if you are not prepared to buy your own genuine unit yourself just yet. I don't necessarily condone pirated things but for testing purposes you could buy and temporarily use Chinese copy of VCDS for ~£30 to evaluate and see if you would like to buy genuine kit. Or possibly try some alternatives like OBDeleven which receives good feedback but I have not used it myself so cannot give any feed back on that.