Hyundai Repair: 1998 hyundai elantra, fuel pressure regulator, hyundai elantra

Question
sometimes the car will turnover and over but won't start. and it also stops while driving.have changed the battery and cleaned everything.

Answer
Presuming your check engine lamp isn't coming on, my first recommendation is to check your fuel pressure while the problem is occurring.  I'd suspect that you may have a faulty fuel pressure regulator, allowing the fuel pressure to be bled off into the fuel tank.  

If your check engine lamp is on, you should begin by reading the stored trouble codes.