While running my ground testing, during the winters using auto
fuel.  I used clear 3/8" tubing for fuel line, from my Facet
pump up to my carburetor.

While the engine was producing power, I noticed bubbles in the
line, on the pressure side.  Baffeled by how air could be
leaking
into a six psi line, I looked it over, and discovered that there
was a slight kink in the tubing.  The bubbles were from the
small restriction in the pressure line (come to think of it, it
may have been a three psi pump, not six).

Anyway, the bubbles really don't bother the Carter carb, with
a float, but, I wonder how much vapor bubbles are returned
from the EFI pressure regulator.  It seems likely, that with
a 35 psi pressure drop, the vapor may be very significant.

Certainly, someone on this list must have a setup capable of
testing the theory.  All one would need would be a clear vessel
to return the fuel to, and perhaps suck fuel out of, with the
remaining system intact.  Pump on, engine off would seem the
worst case.  Cold weather auto fuel would be the most likely
to vaporize.

Test results could contribute to safe fuel system design.



George Graham
Mazda Rx7ez N4449E
Homepage <http://bfn.org/~ca266>

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