Car will crank but will not start.
 

3 months ago I replaced the Cat and Combustion Sensor. One day I try to start her but she would just crank. The fuel pump vibrates when I crank so I don't believe it is the pump. The car is a 2000 Elantra. She was running strong prior to this day. What could it be? I don't have a Scanner. Can you help please? Do you have any suggestiongs for me. Or have you ever heard of something like this. How can I test to see if I am getting a spark? It may even be an ignition coil, do you think :confused: