1993 Plymouth Voyager Ingintion

This Van has been the longest lasting car I ever had. But now when I turn the key there is no resistance (as if to start). The key works the way it should (it does not turn all of the way around, but stops where it should when attempting to start). The van will not start. I bought a new cylinder lock & key, but when I took the ignition switch off, to remove the old cylinder, the ignition switch & cylinder lock & key appears to work properly. Should I replace both any way? What else could it be?