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Bill: Welcome to the Coupe community. I have found that these sort of
problems can be solved by adjusting the venting on the fuel tanks. I do
not
recall how many times the design was changed on the tank system, but
suffice
it to say, several.
Some systems had only one vent (the header tank) others had all
three
tanks vented. I have found that the size of the vent hole in the fuel caps
varied as well as the size of the lines and the routing.
From what you have described, I assume that you have a system that
has
all three tanks vented through their fuel caps and that the fuel return
line
from the header tank is teed to return fuel to both wing tanks. I would
check
the tightness of each tank's fuel cap and try to make them as even as you
can. Also make sure that all the vents are open. I would try swaping the
RH
and LH tank caps, but I suspect that this may not solve the problem. If
not,
then temporarily plug the vent in the left wing tank cap and make some
test
flights to determine if this solves the problem.
I had this sort of thing happening on the last Coupe I worked on. I
had put rebuilt Alon style fuel tanks and plumbing in it, and the fuel
would
spew out of the RH tank cap. I eventually solved the problem by plugging
the
vent hole in the LH wing tank cap. I have had others that I had to change
the
venting on. Sometimes it is as simple as moving the fuel cap from one wing
to
the other. In one case, I actually had to extend the vent on the header
tank
up into the air stream due to being partially blocked by the way the top
cowling and grommet rode in flight.
As long as you have the tanks plumbed together, the system will
perform OK with only one tank being vented.
I have noticed the different size nuts on the fuel valves also. I
suspect that ERCO bought in quantity and that one batch had different size
nuts and threads. Or maybe all of the originals were that way.
Lynn Nelsen Frostproof, FL.
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