By sitting for awhile , what do you  mean? A year or two? If so, you should
do more for your van.Especially if it is still really cold.Perhaps the oil
is so thick the starter wont crank the engine.10w30,or 10w40 to get it
going. Then thicken the oil up  with STP . www.vanagonauts , I think, has a
section about bringing a vanagon back to life after sitting for awhile, or
after you purchace a new one. What you should do to get it right again.
Other vanagon  sites also have this info.Dont know them off hand. Mostly it
is changing fluids and rubber stuff,but it will give you confidence in your
van.

If it ran when parked, it should run when a new battery is
installed.However,this is if it was maintained well before being parked.If
it wont start when a new battery is installed, suspect that the gas
petrified in the injectors, and they cannot spray gas now.They need to be
removed and cleaned.Wiggle all the ignition wires as the corrosion may
cause a blockage for electricity to flow.Let us know how it goes.