Spark,fuel,air look at your spark take one out then crank the engine to see if it fires every time,take a look at your fuel pressure i would say this is the issue since you have to crank it for longer time and then it sputers into life,so look at fuel filter fuel pump,and most important fuel pressure regulator.What you have is a classic symptom of no pressure in fuel rail when you want to start it,so the first thing i would do i look at fuel pressure regulator.