It is possible the fuel pump could have deteriorated over 10 years. Start with a general diagnostic. Air filter, spark plugs, ignition wires, distributor and check for spark. Check the fuel pressure on the fuel rail. I'm not sure what it is supposed to be (35 - 50 psi is typical) but if the pressure starts out low and takes a bit to build up and then begins to drop off after cranking, the fuel pump could be the culprit.
How long since the fuel filter was replaced? A restricted fuel filter can cause this issue. I was surprised to see my MasterAce Surf has a drain plug on the fuel tank. Does yours? Drain the fuel, looking for rust or other debris that might be in there that could plug the filter or fuel pump. If rust is present, you'll need to address that. If it is dirt and debris, clean it out and change the fuel filter. You should be able to clean any debris from the fuel pump.
The van sits quite a bit. It is possible you might have a stuck compression ring. Remove the spark plugs and spray a bit of WD-40 or other penetrating oil into the cylinder. Let it sit a few minutes, turn the engine over by hand. Add a bit more, let it sit a few more minutes then turn the engine over with the starter to blow the penetrating oil out. You should get a bit of fuel too, unless you pull the fuse for the fuel pump. Install the spark plugs and try to start.
If these things check out, it might be time to check the valve adjustment. Toyota valves are typically shim adjusted. Your shop manual will have the valve measuring procedure and the tables for identifying the correct shim.
Good luck.