Fuel Pump Failiur?

What are some signs of fuel pump failiur? I am having trouble starting my car when its been warmed up. If i put the key to ON so it pressurizes the fuel rail and wait about 5 sec i try to start it it is hard to start takes like 5 sec. if i flick the key to ON then Start instantly it starts up really fast and normally like its suppose to. So based on that i know its not ignition cause ive rechecked everything 10 times. Is my fuel pump just not holding pressure it drives fine dosent stumble or anything its just with start up. I remember reading a while back that air bubbles can get in the system when the fuel pump starts messing up and thats whats causing it to do that but i dont know anybody help me out?