1) I have a check engine light and it throws a fuel code. What all areas of the fuel system can trigger the check engine code?

2) If i let my car sit for over 10 or more hours, it doesnt want to turn over. Sometimes when i hold the key all the way over for about 10 seconds, it starts fine. Other times, it doesnt do anything.
5 out of 10 i get this problem. But once i get my car started and running, i can shut it off and cut it back on with ease...any suggestions?