Why does my car take longer than usual to start?

Hey so my 91 buick century, 2.5 l4 takes a while to start, I let the fuel pump start up, after that I crank and it takes a few seconds to start, especially when it's been sitting for an extended period of time. Have checked the battery, alternator, charging system, and spark plugs are just fine, and replaced the plugs. Still the issue persists, fuel pump by chance? I'm not sure. Would like some help, thanks!