Ray,
A lot of certified aircraft, usually low wing aircraft have a mechanical pump
on the engine and an electric pump for start up, takeoff and landing. The
electric pump is turned off during normal flight (unless the mechanical pump
quits of course). There is a bypass system though. There is a way to hook it up
that is dangerous that some have done in the past and I must be getting old
because I can not remember the wrong way that looks correct. Maybe if I sleep
on it I will remember but I do know one thing and that is that you do not want
only a single fuel line from the mechanical pump going to the carb and the
electric pump only pumping to the mechanical pump if that is your question. I
will take a shot here and say that you just place a T fitting in the carburetor
fuel inlet with the electric fuel line attached to one of the inlet legs of the
T fitting and the mechanical fuel pump line in the other. As Mark said there
should be a one way valve just on the engine side of the
electric fuel pump to keep the mechanical pump from pumping gas back through
the electric pump. The electric pump may have such a valve built into it, I can
not remember. My old Mooney is set up this way. On the other hand my old
Bonanza has a pressure carburetor on it, the closest thing to a fuel injection
system in the old days. The pump supplies more fuel to the carb than it uses so
there is a return line back to the left main tank for the excess fuel. That is
why when you fly a Bonanza you always takeoff on the left tank, this is
assuming your left tank is full of fuel when you take off so you can free up
fuel tank space for the returning fuel by burning that fuel first. If you were
to takeoff on the right tank or auxilary tank for example while the left tank
is full, then all returning fuel to the left main will be pumped overboard
through the vent line.
Someone correct me if the hookup I described is wrong.
Larry H.
I have an 1835 VW engine, with a Facet fuel pump feeding into a Bosch
mechanical fuel pump. to an EFS-2..
Will fuel flow through the mech, pump when it (the Bosch) is not pumping?
Ray Goree
Ray Goree
817-795-4779
