Progress on non starting 4.3

I posted yesterday my 2000 Astro 4.3 would not start. Turnover but no start. Today I added 2 gal. gas to 1/4 tank and engine started but now very rough running at all rpm.

This era of Astro, as well as many other GM vehicles, is notorious for fuel pump/sending unit failures. Do a fuel pressure check for running fuel pressure and rest fuel pressure. If running pressure is low, and rest pressure quickly drops to zero, you have a check valve in the sending unit that has gone bad. Many parts stores have aftermarket check valves you install inline along the frame rail to correct this problem. Since you added 2 gallons of gas to 1/4 tank and got it to start, I suspect your sending unit may be bad also and you were actually out of gas. Many GMs of this era have experienced sending unit failure of this nature, where the gauge will read 1/4 tank when it is empty.

Thanks a lot. This gives me a course of action.