03 starting problem

[glendale]

ok i have a 03 tahoe 6.0 awd. it sarted as a every once in a while thing.when you get in to start it it will fire and then die immediately. you can sit and just keep doing it. if you leave it for about 15 minutes it will fire right up. it has about 140,000 miles on it. so my first move was the fuel pump bought from the dealership. next i did the starter and battery (just happened to also go it).it is happening more frequently now. and my wife has my two kids around with it. i today removed the after market alarm with remote start and no change.please help.