1997 chevy blazer new pump and filterstarts can hear prime but in morning start after couple tries

Check air filter and clean throttle body add Lucas Fuel Injector Cleaner to gas tank.

the reason your truck isnt starting right away is the fuel pressure is bleeding off. this truck with the style of injectors wont fire unless it has 56 psi or better in the fuel rail chances are the fuel pressure regulator has a leak out of the vacuum port which if left alone can, and mostly will damage the motor how do you tell get someone who has a fuel pressure gauge hook it up to the fuel line shredder valve start the truck the pressure should build to 63 psi and hold at around 55 psi while running shut it engine down and watch the fuel gauge it should hold 55psi or better for over 10 minutes and longer (if the engine is hot the pressure may actually build due to expanding fuel from the heat) if the pressure is lost you then have to figure out where it is going either the regulator or a leaking injector

Or may just dirty injectors causing fuel to leak by.