For any year Vanagon engine management system operational problems,
reference the VW Fuel Systems Pro Training manual.
It has an excellent step by step diagnostic trouble shooting guide that
the Bentley or Muir's book doesn't even come close to covering.
It'll get you to the root of the running problem fast and it's easy to
read.
If you own a Vanagon, this instructional "How to" manual is a pre
requisite type item, or should be anyway.

RC