just won't start

[C2996]

My b6 s4 will not start, battery is fine, everything electical works, it just won't fire up, although very occasionally and randomely it will.

any ideas?

[Tame Technician]

When its not starting, what does the rev counter say at starter motor speed.

When it randomly starts, what does it say.

I'm guessing crank sensor, if it is the crank sensor, the rev counter will show no revs when cranking on the starter, when its failing.

IT will show, arround 200 rpm when it starts.

[C2996]

I'll have a look and se hat it says

[Dr G]

Purely to clarify; the car is turning over when you twist the key?