I posed this question a while back and the responses were similar.  Seems we
have a bit of a dilemma.  As our vehicles approach 20+ years the threat of
rust and crud in the pump increases while a pre-pump filter can create the
aforementioned restriction issue.  I'm wondering if the restriction issue is
only a problem once the filter starts to clog.  If so, seems you could have
the best of both worlds by changing it frequently.  I guess the question is
at what interval and how do you know when it needs to be changed before you
encounter running problems?  Assuming the condition of all tanks and the
amount of contaminants varies from van to van.  But I guess for $5 for a
square filter you could order a stash and keep them on hand without too much
expense.  Seems like cheap insurance for the expensive pump and round
filter.
Mike
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" .....The small filter before the pump has the disadvantage of being a
restriction on the suction side of the pump increasing the chance of
vaporizing the fuel before the pump and causing various running problems.
Except for the in tank screens, most cars these days do not have filters on
the pump inlets."
.
"Aging, rusting gas tanks were apparently not considered (that's a
post-warrantee problem :-)".