Kris the folks are on the right train of thought with the fuel system.
You are pretty much guaranteed it is not electrical (starter, altenator or battery) by the fact that it turns over. The clue to a possible fuel system problem is the fact that it will start. In other words the electrical is doing its job, but there isn't anything to ignite, ie fuel.
There are some other possibilities as was eluded to with the ECM (Computer and other "brains" within the engine management system). I would go with the fuel system first.
What sort of mileage is on the van? Has there been any significant repairs in say the last 2 or three years? Specifically in the engine, not brakes or frontend type jobs.
Just to be on the safe side and I am not trying to be a smart ass, but do you have gas in the tank?
I can also recommend Suburban, good guys there, Also in Oshawa Franks on Valencia, down by the motors