2000 Pontiac Grand Prix started fine last week and drove fi

I have a 2000 grand prix GTP, and I just put a new fuel pump in it last week, well the car had some problems starting, like I would crank the engine for like 5 sec and no start, but if I would wait like 10 sec and try again it would start and I could drive around fine, but if I would leave the car set, "like overnight" the car wont start at all, but I got the car to start for like 3sec"there was a strong smell of gas" and the battery light came one after it stalled out, so I checked the batter and there was 12.3volts or something like that, and then I checked the spark plug wires and they were fine and then the spark plugs and there was spark and when I pulled the spark plug out there was a little bit of gas on the spark plug, but the car ran fine for a week after installing the new fuel pump, but I did have a few problems with it starting, but I would start right up after you just got done driving it, but like I said if you leave it set it takes 2 tries to start it, but today it cranks but wont start?