I have a 2008 silverado 1500 flex fuel and has cylinder management and recently it will not start until you cycle the key a couple times or you have to pump the throttle to get it to start other than that it runs fine once it starts it acts like it has no fuel in system or the fuel pump is not working right.

 

Fuel pump is not holding the pressure when turned off. The check valve in the pump is bad. You can replace the fuel pump or add a check valve in the fuel line.