Wiring up the fuel pumps

25 Jul 2004 Wiring up the fuel pumps

Update 20210918: I didn’t install the Eggenfellner Subaru engine, so any post that references that can be ignored or used as a cautionary tale about how to avoid wasting many years and $50k.

The Eggenfellner Subaru engine has two fuel pumps, and some additional logic to ensure that there is always fuel going to the engine. In order to ensure no single point of failure, I’m considering deviating from the install manual, and have two switches for the fuel pumps.

The basic idea is that the power for the fuel pumps will come directly from the battery busses, to their own switch, and for the AUX pump, there will be a relay and pressure sensor to activate the AUX pump if pressure falls below a certain threshold.

The install guide specifies a single switch to choose either the Main pump, AUX pump, or Automatic activation of the AUX pump. I feel that splitting this function into two switches will add a bit of reliability and simplicity, at the cost of a small amount of operational complexity.

I’m trying to design my panel so that normal flying conditions will have all switches in the panel “UP”.

Here is a diagram of what I am trying to do with the fuel pump wiring. Click the picture to enlarge it.