[Beav]

If you look closely at the crank pulley (dampener) you'll see it has a center hub and a separate sheave (pulley) section. They are held together by a band of rubber between them. Make a chalk or crayon mark across the two pieces, start the car and do whatever it is you do to make the problem occur. Then shut the engine off and check the chalk marks. If they are no longer in alignment you'll need a new dampener. There are a number of pics on this site of what the dampener looks like when it separates, use the search feature.