1994 Mustang gt. cranks and tries to start

Follow the no start checklist liek General karthief said. Sounds like weak spark to me. When you say ignition module i assume youre talking about the TFI. If you picked up a replacement from somewhere like autozone id try to get another one and see if that makes the difference. I know ive had bad luck with them as have some other people where you can get a brand new one and it be bad right out of the box. The other thing to check would be your coil. Have you pulled codes? Sometimes that will give you an idea of where to start