If you can get a mechanics starter test lead from a local flaps... unless you already have one... attach one of the alligator clips to the power lug on the starter and the other to the ignition connection on the starter solenoid... when you push the button ( key on out of gear) the power goes directly from the battery to the starter solenoid ... if it pops right off ...the problem is in the ignition circuit... if not ... gingerly jump out the two large posts on the solenoid... one is the battery supply lead the other is the starter winding... if it starts ... the problem is in the solenoid... if not... get another battery ( borrow buy or beg) and jump the positive terminal to the battery post on the starter... jump the other post to a good chassis ground... (not the negative battery post) ... If the starter pops the engine over.. the problem is in the battery or the battery cables... if not your starter is the last option.. The vanagon positive battery cable is 10 feet long and notoriously light weight... the ground circuit is even worse because it is a cobble of connections... check the ground strap at the transmission closely... take it off clean the metal surfaces with emery or some such thing... on my own van I ran a #4 wire from the trans to the negative post of the battery and a # 2 wire from the battery to the starter... no more starting problems for me...