Chrissi wrote:

I need to implement some form of cam /microswitch to manage the pumps as I do not want to have some
situation where the pumps are on but the sump is not being fead. I was going to vent the sump to the
tanks and vent the tanks, this prevents any vapor accumulation in the sump after initial fueling.

If the pumps both draw from the sump, and the fuel valve controls which tank drains (i.e. not force-fed
via another pump) into the sump, and the fuel rail excess is dumped into the sump, then it really isn't
as critical for the fuel valve to control the pumps (versus Brian's system where it is much more
important).  What is more likely to bite you, Chrissi, is that your system will crossfeed fuel (via the
sump vent) when parked on non-level ground with full tanks.  This means that fuel may stream out the low
wing's fuel vent.  Try to put the tank vents as high as practical.

Alternately you could use a six-port valve to return the vent to the draining tank(s), which will also
allow the vent to be "off" when the supply is off.  But if you're going to go to the trouble and expense
of the six port valve, you might as well plumb the fuel rail excess to it instead of the sump vent.

Russell Kent

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