Have a 1999 chevy astro van 4.3l that will only start with carb cleaner?

Pull a spark plug and check for spark. Refer to my suggestions on the Honda that wouldn't start for more details.

There has to be a fuel proublem. It's not the spark or anything because you said it does run. Check to see if your fuel pump is working. Check and see if the fuel lines have fuel presher in them. You can do that by losening the fuel line or if it is fuel injected there is a valve stem looking port in the fuel rail, simply push the center pin in and it should spray fuel. Also check to see if you need fuel the filter. It could have more than one. Check to see if it has fuel on the engine side of the line and if not check the tank side of the line.

It is your fuel pump, to replace it, you have to drop the fuel tank and it sits rite on top. its also a good rule of thumb to replace the fuel filter too, as this will make the pump last longer if you did not change it before. i believe the filter is supposed to be changed every 30k.

Most likely the fuel pump , change the filter at the same time.
gm has had fuel pump problems for years. also if the new
pump comes with a new plug , use it.