Starts but then dies

[Shaned]

I have 1988 6.2 with 43000 original miles. I have had the truck for about 2 years. It has always started and ran great until about 3 weeks ago. It starts and runs for about 30 seconds and then dies. It is real hard to get it to start again. Once started it runs fine. If I let it set for over 30 minutes it will do the same thing, start and then die. I replaced the fuel pump and fuel filiter this past weekend. Still the same problem. Any suggestions.

[highpockets]

I had this problem two years ago. Turned out to be a slight air leak into the fuel system between the tank and lift pump. Look for a slight fuel drip or leakage. My filter drain didn't seal correctly and leaked fuel when stopped and air seeped in when running. Lots of white smoke. Ran great on the road.
Sometimes the problem is just too easy to see and I saw the wetness and dust on the valve but it just did not dawn that AIR would follow the same path.