You should also clean and re-tighten all of the ground cables located in
    various places around the van. Particularly the transmission to frame
strap.
    I think it is most related to starter peculiarities also the one from the
cyl. head
    to the body. Both a source of starter problems for me. I changed out the
    starter with remanufactured Bosch units 3 times (not fun on a syncro)
    before figuring out the bad grounds.
    Cheers
    ROB '91 syncro