1998 S70. My driveway has a slight to moderate incline. When I leave my car overnight on my driveway, it won't start in the morning. Acts like it's not getting fuel. If I coast it down to the street which is level, it will eventually start. If I leave it overnight on the street, it starts up fine in the morning. I'm thinking it's the rollover valve? Any thoughts? Could an amateur mechanic (me) replace the rollover valve?

 

I don't think it is a rollover valve. That only has fumes going through it.
The pumps usually have a check valve in them.