A few years back mine did what you are describing. On mine the main heavy ground cable was not making a good enough connection. I was fooled by my volt meter because I had one lead of my meter outside off the engine on the frame of the bus which gave me my voltage. After taking a voltage reading from just the motor / starter I then had to add an additional heavy ground lead to the bus frame, which gave enough voltage to the starter. 
Hope you get it soon.
Kevin Plichta
 

> Date: Wed, 20 Jun 2012 21:02:01 -0400
> From: ckelmo1@COMCAST.NET
> Subject: Engine out, now in: won't start
> To: vanagon@GERRY.VANAGON.COM
> 
> Of all the things I did while the engine was out, I didn't touch the starter since I replaced it only a few years ago.  But after re-installing the engine, I get nothing:  no sound, no click, nothing.  I tried jumping the battery and that made no difference at all.
> 
> Is there some basic wire I may have missed in the reinstallation?  I took the starter out and the gear turns easily enough by hand, so it's not jammed.  
> 
> Summer is ticking away...
> 
> Cecil
> '85 Westy "Der BrotKasten"  now more like a breadbox than ever...