> Very few modern-fuel injected cars have filters before the 
> pump. The main problem with a pre pump filter is that any 
> restriction on the suction side of the pump will create a 
> vacuum and cause the fuel to vaporize or even boil at the 
> pump inlet. Particularly in warm weather this can create 
> vapor lock problems, intermittent, unexplained fuel 
> starvation etc. This is probably why VW discontinued the pre 
> pump filter although vapor lock is rare on these vehicles. It 
> is a major nightmare on some of the CIS cars. 

True, but as you say, not on Vanagons  Virtually every fuel injected Bus or
Vanagon has this configuration (all fuel injected busses and almost all
Vanagons except mid 1990 to 1991), yet vapor lock is almost never reported
on either the Type2 or Vanagon lists.  If this were even a remotely common
issue on Vanagons we'd be hearing about it often, or at least sometimes.
(Also, I've never had a customer who added a pre-pump filter and then
reported a vapor lock problem.)  I think this is a case where VW was simply
"fixing something that wasn't broke." However, I recall reading on the list
that VW offers a small bypass hose that does the same job (different inlet
and outlet size) for those who prefer that route, although I'm not sure of
the part number. (Also I have a sample coming of what the supplier _thinks_
may be an aftermarket 90-91 tank. If they do offer it I'll keep one or two
on hand. But I am not confident that this is really what it will turn out to
be. I think it may be a European spec tank.)

- Ron Salmon
  The Bus Depot, Inc.
  www.busdepot.com
  (215)  234-VWVW

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