Posted for "terrence o'neill" <troneill@charter.net>:

 So, Bob , when one tank runs dry and you say 'one side sucks air, it provides
the lower pressure drop in the line and the pump sucks mostly air' ...
 What is the significance of '...the lower pressure drop in the line'?  Does
this mean the pump for the other, fuelled line will pull air through the
crossflow valve and lose its prime?  Has anyone tested this?
 Thanks for your patience with fuelsystem-challenged me.
 Terrence