norm Muzzy wrote:

So, how about this:

Put an injection pressure pump from the left tank to a junction block

that

feeds the FI manifold,
another injection pressure pump from the right tank to the same junction
block,
return from the pressure relief valve to a return tank (perhaps 2 gallon
capacity),
there are a pair of solenoid valves at the top of the return header

tank.

When the left pump is on, the solenoid valve that allows the fuel to

return

to the left tank is open.  When the right pump is on, the right return
solenoid is open.
Place an orificed line around one of the solenoid valves to provide a

fuel

path in the event that both solenoid valves die.

Standard pocedure says to only run one fuel pump at a time, but if one

of

the solenoid valves would fail, you could run both pumps so as to keep a
return path open.

Now-  with the return header tank you have an option.  You can install a
third injection pressure pump on this tank to give you a 'last ditch

supply'

of 20 minutes of fuel or so.  Such that if you drain the left tank,

drain

the right tank, you now know that you have a certain fixed amount to

find a

place to put down.

Failure analysis-  You can loose any two of the three pumps and still

have

power-  right up to the point that the tank feeding that pump goes dry.

All of the tanks are independent of each other, such that a birdstrike

that

takes out the bottom of one of the main tanks does not create a drain on

the

entire system.

If the return solenoid valves die, the orificed line keeps the pressure

from

going to pump regulated pressure, it would return to a default tank.

The

orificed line also serves as a vent for the header tank should you

utilize

the third pump in a fuel emergency.

One of the problems with these Bosch FI pumps is that they circulate a

lot

of fuel, and returning them to a same side tank all of the time will
overfill that tank.  But with a plan that consideres where the fuel ends

up,

I suppose that you could return to one side only.  I like the idea of

using

a second FI pressure pump rather than a transfer pump, as it gives you a
backup.

Questions, comments, or concerns?

Regards-
Norm Muzzy

norm doty wrote:

this way to complicated, to many ways the fuel can be blocked or routed
wrong.
remember the K.I.S.S. principle.
Norm Doty

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