2000 Ford Ranger wont stay running

I just rebuilt the bottom end. The truck has been sitting for a couple of years. It will start, but dies immediately. It sounds good when it starts, but just dies. The scanner tool reads NO CODES.I have checked and rechecked all connections I cant find a problem.I did notice a little fluid coming out the tail pipe, I think it was gas but unsure. New fuel filter and I replaced the old gas with new and have fuel pressure at the fuel rail. I know im getting fire because it starts, it just wont stay running. HELP!