If you are grounding the 2nd battery to the frame as usual instructions
state, then you have a good ground.  I would suspect the old ground wire
on the new primary battery.  Try grounding the primary battery with half
the jumper cable set and see if it will start the van.  Bet it does.
Also check the ground wire's connection with the battery and the body of
the van.

A failing ground wire that wasn't properly diagnosed was the culprit
with my ex's Mazda years ago (when she wasn't an ex).  I don't remember
all the details, but it involved the probably needless replacement of
the alternator, failure of a new battery in a few days, and they were
about to replace the starter.   And all that was wrong was the ground
cable - which in fairness ran a long way and disappeared behind some
engine stuff where the break had occurred.

This was before I had learned as much "car logic" from this list, but it
finally dawned on me that it was always starting just fine when jumped
from my Vanagon (more van content), and that I was grounding to the
frame not the battery when I jumped it.

Sam

--
Sam Walters
Baltimore, MD

89 Syncro GL, soon to have SA suspension and 15" disc brakes
85 Westy Weekender, new to me 8/01/03
84 Vanagon, original owner, soon to be retired, just too many problems

All incoming and outgoing email scanned by
automatically updated copy of Norton AntiVirus.