The problem with the "goo" coming out of the heat sleeves on Vanagon fuel
injection lines might be related to the permeability of the fuel hose
itself.  If a substandard hose is used, fuel might be passing through the
walls of the hose and then remaining held in contact to the sides of the
hose by the heat sleeves, thus causing deteriorating of the outer cover of
the hose.  If this fuel contains a significant amount of alcohol the fuel
will be even more destructive toward hose material not designed to tolerate
the new blends of gasoline.

SAE30R9 spec hose (i.e. fuel injection hose) has a permeability of
15g/m2/day and SAE30R7 hose (i.e. non fuel injection fuel hose) allows
550g/m2/day to evaporate through the walls of the hose.  This is 36 times
the limit for the correctly rated SAE30R9 fuel injection hose which has an
additional barrier to prevent seepage.

Gates describes their SAE30R9 hose as in the following way
(http://www.gates.com/common/downloads/files/Gates/brochure/TechTipsForm.pdf ):

"Gates SAE30R9 hose uses a laminated tube of
Fluoroelastomer, as a thin wall inner layer backed
by traditional compounds. This first layer protects
the rest of the hose from attack, swelling or
permeation from aromatics, oxidized gasoline (as
can occur in fuel injection systems), ethanol or
oxygenate additives and a wide range of petroleum
based products."

Neither SAE30R7 or SAE30R9 hose is designed for total emersion in fuel, as
is SAE30r10 hose that is designed for in-tank fuel pumps, but since SAE30r9
hose seeps much less fuel it is likely much more suited than SAE30R7 hose
for installation with an impervious cover like the heat sleeves.

Much of our gasoline today contains additional amounts of alcohol that will
attack and cause swelling of many rubber products as we have been warned by
some automotive manufactures.  It is more important than ever to use hoses
with the proper specifications for use with today's fuels.  Many of the
rubber products in our 20+ year old Vanagons were designed when alcohol was
not a significant component in our fuel and therefore were not designed to
stand up this new attack.  As a result, products that we have "used for
years and never had any problem with" are now inappropriate for the same use
and may unexpectedly fail.

One indication of this change in fuels is that Weber Carburetors has had to
change the range of jets in their JetPak tune-up kit twice in the last few
years because the increase in alcohol in gasoline results in excessive
leaning out of mixtures.

Times and fuels have changed and we must make changes in our selection of
fuel system components to keep our buses from burning.  Make knowledgeable
and smart decisions when replacing your fuel lines.

Ed McLean