Rough initial start Runs and Starts Fine afterwards

I have a 2005 Nissan Frontier.

If the vehicle has not been running for several hours it requires two or three, 3 second, start attempts before it will start and when it does start sometimes runs rough for a minute or two. The problem seems to be more pronounced when the gas tank is less than 3/4 full. This vehicle also has a fuel sending unit problem OBD code 0463.

Check the fuel pressure.

Maybe the fuel pump check valve is not holding. This is designed to maintain residual fuel pressure while the car is parked.

If it bleeds off air will be present in the fuel lines. This will cause slow starting and stumbling until the fuel pressure clears the air out.
(Think of a garden hose with a tiny leak lying out in the sun on a hot day. Eventually the pressure in the hose will die down, air pockets will form, and the hose will sputter and spit until the air has been purged.)

Found a loose line going to the evap test port, looked attached but was not clamped on the fitting. Appears to have fixed the start problem. OBD 0463 seems to be a common problem with Nissan vehicles between 2005 and 20007.

Thanks for the suggestions.