blazer will not start

ok, while driving the vehicle just stops running and will not start up. A few days before I put it into park and it would shut off, with the key still in run position. Didn't do it after that for next couple of days. I changed the battery, distributor, coil wire, coil was replaced a few months ago. I do have a spark. I have yet to check fuel pressure but I do hear the fuel pump running after I turn the key on. The engine cranks but it sounds like it loses power a little bit at intervals. Is it a short or the ignition switch? If anyone could help I would appreciate it. Thanks

oh yeah......its a 1999 bazer 4x4......he he he

Check the fuel pressure.

Check the condition of the plugs.