Got a '96 blazer with the 4.3. It starts hard. Changed plugs, wires, cap, rotor, fuel filter, checked air filter, checked fuel pressure. Crank it in the morning and it mite skip and then just crank. let off wait for the pump to cycle and then try it mite cough then just crank, then it just cranks. Wait a min. try again. Usually have to jump it. Have a Snap-on MT2500 scan tool but not codes, EVAP codes once in a while but thats it. Once it starts its fine. Would start back up fine all day as long as it doesn't sit for more than 5 hrs. I'm just about out of ideas. Do you have any?

 

Test the fuel pressure, specifically the bleed down. It is possible that the system is bleeding down, flooding the motor. You want to monitor the fuel pressure when you are having this problem.

Does holding the throttle to the floor help it start?

 

I did test pressure it was with in spec. Didn't bleed off after I fixed a fuel leak by fuel tank. Now it stays after pump turns off. No holding pedal to floor dosen't help.