1991 Chrysler 5th Avenue engine cranks but wont start

Electrical problem
1991 Chrysler 5th Avenue V6 Front Wheel Drive Automatic 53000 miles

when I try to start the car the engine turns stongly, but it wont start for an extended period of time. Some time it will after a few tries, sometimes I try and try and nothing for a long time. There is fuel in the fuel rail with good pressure. This is a new development after I recently had a cam sensor replaced, and one time when it was happening I popped the hood and saw a vaccum line had come loose.
any ideas thanks much