[20GMC00]

I have an old body style 2000 C2500 with a 5.7. It has been getting harder to start. It has a new Delphi fuel pump and new battery. I need to crank it 4-5 times before it will start sometimes. Sometimes it won't start at all. I found out that if I put a 10 amp battery charger on it for just a few seconds, it fires right up. Also I have my live data scanner plugged in and it is staying in closed loop all the time and both rear O2 sensors are staying at 99%. It runs fine but it's just getting harder to start. Has anyone ever had this happen or have any ideas? Thanks!