engine is cranking but not starting on 1991 GMC S15 Jimmy

one day the truck decided not to start anymore, the engine is clearly cranking but it wont start, i changed the fuel pump and the fuel filter but the truck still does not start. if you know of any other reason why the truck would do this please tell, any advice or information will be helpful.

Asked by for the 1991 GMC S15 Jimmy
Have you checked to see if you are getting spark?
i dont think i have, how would i do that?
If you have a timing light or know someone who does that would be the easy way. Hook it up and pull the trigger while cranking the engine if it pulses you have spark. Test more than one wire. A spark plug tester could also be used.