Russell Kent wrote:

Yvon Cournoyer wrote:

Until now I have operated my 1986 - 13B with a single fuel pump on the
Holley fuel injection system. I now wish to install a second fuel pump,
essentially for more security. Holley FIS is a low pressure system (I
operate at 13-14 psi) with excess fuel return to a single fuel tank in
fuselage. In spite of the abundance of info on these lists, I still do not
know which is more practical; an installation in series or one in
I asked Holley, but they are/were no help. I should have asked here first.
HELP! Please.

Paul Lamar replied:

Parallel Yvon with a switch so you can select either one.

The longer answer, Yvon, depends a little bit on the fuel pumps you use.

Start by plumbing separate pickups & strainers to separate fuel lines all the
way to the pumps.  Then if the fuel pumps have integral backflow check valves,
then the fuel lines to the pumps (i.e. "in parallel"), plumb the pump outputs
together and then to the Holley system.  If your pumps do not have integral
backflow check valves, then you need to get 2 check valves, and plumb the valves
downstream of the pumps, but before the point where the pump outputs are merged.

Be certain that your return line has the capacity (i.e. inside diameter) to
return 200% of the rated flow of one pump (which is very close to 100% of two
pumps).  Wire the pumps to a "left-right-both-off" switch in the cockpit, or to
two separate on-off switches in the cockpit.  Takeoff and land in the "both"
position (or both individual switches on), cruise on "left" or "right" (you
should make an effort to keep the pump running times roughly equal over the long
term).

Finally add "individually test fuel pumps" to your run up procedure (sort of
like the mags test).

Russell Kent

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