Hello audi members

I have a audi a4 from 96 which have some start issues..
So I decided to change the spark plugs, which was a good idea, after the change were their no start problems anymore, next day did i decide to drive a while but that time i was trying to start the car was there no cranks, i hear the starter is running and every lights are ok in the dashboard, i have also tried to jumpstart it, but it won't start/crank?, the starter has also been replaced (secondhand)
I have searched a lot but can't find any solution for this problem..

do anyone have an idea?

/Abiran

 

So the starter spins, but the engine doesn't. That means either the solenoid is pushing the starter gears out into the flywheel teeth, the starter was not shimmed so the starter teeth can engage with the flywheel teeth, the flywheel teeth are worn flat in that spot and the starter can't engage with the missing teeth, or your flywheel is broken loose from the chrank shaft flange (probably little chance of this). Do you hear any grinding noises when trying to start it, or does it sound like it always did?.