I would think the IPR, unless you got a bad CPS sensor which happens1995 7.3 diesel. Today it was difficult to start in the AM. In the afternoon it starting stuttering and stalling. It would start right up after and drive for a while and then do it again. I got it home and changed the CPS and it wouldn't start at all. Changed the fuel filter and still no luck. It just cranks and cranks. I few times it sounded like it would turn over but no luck.