Engine not firing
sounds like a fuel related problem, possibly a fuel pmp, take a little starting fluid and spray it into the air intake and try to start it, if it fires up for a couple seconds then it is the fuel system...if it doesnt start that you have an electrical problem. Once you narrow it down into one of those two catragories, you will know where to look....the most common problem in fuel system is the fuel pump, others include, the fuel filter, fuel pressure regulator, and the injectors, the most common eletrical issues are the plugs, wires, coil, distributor, and starter. Another good way to check a fuel pump is to have it nice and quite and to the key from off the the start position, not turn the van over, but just to start, you should hear a little humming noise from the rear of the vehical which is the pump kicking on, if you can acheive the quiet you need for this you can have someone turn the key back and forth while you listen at the filler tube or even crawl under to the tank.
best of luck, we are here if you need anything else.