Tuff call.Dont know the history on this.Does your van have automatic? If
so, could be a netural state switch out of adjustment.Try starting in
netural or wiggeling the shifter while turning the key (if automatic).I
would check for current to the starter solinoid(one of the  little wires on
the starter),w/the switch turned on ,of course.If no meter, just remove
each wire , one at a time and check for a spark when scratching the wire
on  the post. Is the mo-mo locked up?I think there are 3 wires on the
solonoid.You may need a Bently  to decide which wire is used.Maybe just a
grounding problem.Corrosion is an issue on the wires and grounding
straps.Wiggle each terminal on the battery. Maybe there is corrosion
here.Could be juice in in the battery , but cant get out in enough quanity
to turn the starter motor.Bless the 4speed and coast starting.