I have a 2013 Denali having similar issue long cranks after sitting. Have replaced fuel pump twice plugs and wires twice and still have a long crank to start. Runs perfect once started and I’ve noticed that if I press the pedal to the floor when cranking will fire right up.
I need some other opinions on possible causes. I’m almost convinced that it could be a bad injector leaking but don’t want to keep throwing money at it.
also just to add I do not have a gas smell outside or inside the vehicle. Just smells like it runs really rich.