Jeep doesn't like starting

My 2000 Jeep Cherokee Classic has recently been reluctant to start. All the accessories work fine, so its not the battery. I put the key in and it turns over but doesn't start even if I hold it for awhile. I usually have to let it go, and then try turning it again for it to start. However if its already been running, and then I shut it off, it will start right up. Any ideas?

Fuel pump check valve. Search....quite a few previous posts on this issue.

You can fix it or use a work around.