4.3 I replaced the fuel pressure sensor inside the spider manifold a few years ago as well as new fuel pump. I usually have to pour a little bit of gas in the intake and sometimes it takes a few tries before it will catch and run on its own. My guess is the issue might be its losing vacuum pressure somewhere that it's doing this. I have a parts blazer same year so I can try switching parts if anything is easy. I tried switching intake tube stuff and replaced brake booster o ring. It seems it will start right away after It was just running but if it sits 10 minutes not. If I cycle the key a bunch of times it might start by itself.

 

fuel pump