Will not start after being driven.

My van will start with no problem after it has set over a long period of time and if it has just been setting at an idle but if it is driven even a few miles it will not start. After being driven it will turn over with no problems and fires but spits then dies. If I keep trying to crank on it it will eventually stop firing. I have done a lot of research online but have not found where anyone has found the problem. Can anyone shed some light on this? Thank you in advance.