'99 Silverado Cranking Issue

[CornDog05]

Hello, I'm new to the board, so I thought I would start off with a problem solving question. I have a 1999 Silverado 1500 2wd with the 5.3. The truck has 235,000 miles on it. My problem is, sometimes it acts like it is out of gas when trying to crank it. First thing in the morning, no problem what so ever. It fires right up like it should. But if I drive 10 minutes away and park it for 10+ minutes, then try to re-crank it, it just turn over and over and over then will finally start. I can drive it to work (25 miles away) in the morning and when I go to lunch 4 hours later, it will do the same thing.

It almost seems like it is flooded when it does finally crank, and will occasionally puff a little rich smelling blue smoke. I replaced the fuel pump/sending unit a couple years ago. Earlier this year I replaced all four O2 sensors when it had a "Service Engine Soon" light on.

Has anyone else run into this problem before? I would like to fix it pretty soon because I know it can't be good. Thanks for any advice you can offer.

Justin