1999 GMC

Start by checking fuel pressure with mechanical gauge, next spark.

Do you hear the fuel pump come on when you turn key to run-if so check the fuel pressure to rule out the fuel filter and a weak pump if all okay -check if the injectors are pulsing if okay-test the coolant temperature sensor, fuel pump relay and trhe duel pump and oil pressure sending unit-could also be the injectors and fuel pressure are leaking dropping the fuel pressure causing the hard starts