The blades on my Craftsman 42 " Lawn Mower will not engage when I move the lever upward as usual. I feel like the problem is with one of the pulleys on the mower deck but do not know exactly what I should be looking for. Can anyone help?

Hi,
The most common problem with tese machines is that the shoulder spacer that serves as the pivot for the tension ider of that belt seizes because of corrosion. Remove the bolt and clean(sand) the spacer, and do not wash the deck.
Peace,
Clarke