I have a weird problem with my 1996 Audi A6 2.6 V6.
When the car is towed in gear for a few seconds it will start up. Within 30-45 minutes or so after being run it can be cranked to a start normally using the starter motor. This behavior has been consistent for weeks and has worked over 10 times. When the engine is not warm however it will just turn over at what seems to be a good enough speed but will never start up, not even a cough. The battery is almost new and fully charged, I have also tried jumper cables. My suspicion is that one of the sensors does not provide a correct signal when their temperature is too low.
I have checked ohm/voltage values of crank, cam and coolant temperature sensors and they all seem to be correct. No debris on sensors.
I had the same issue a year ago, replaced the crank sensor among other things and it still wouldn't start. Put the old sensor in and then tried to tow the car to a start. It started up and worked for another year without any issues.
What I am mainly asking for is a way to bypass the sensors to rule them out as the culprit and to find a temporary solution to make it driveable until I can find the actual culprit and fix it properly, possibly by somehow cranking the starter motor without turning the key all the way. If for example someone could tell me which relay engages the starter motor (and where it is, I couldn't find it in the passenger footwell where it was said to be) or what would be the best way to go about bypassing the sensors, possibly by still using the key to turn the engine over. Other ideas are also welcome.