Wont start

I have a 1986 gmc sierra with a 305. Engine rotates strong, but will not start. I sounds like its firing or almost going to start but will not. It has a new fuel pump and filter. It has all new ignition system(distrubuter, rotor, and cap). I think that the timing is not perfect but it should be close enough to start. It did this last week and I checked several things but didnt change anything, and it started and ran all day very well. The other day the engine just died wont start. Any advice would be greatly appreciated.

thanks

khonschevy