Good read on the conversion

Since we do not live in MN and the coldest it usually gets in the winter around here is low 30's give or take, my brother doesn't want to loop the fuel return line. His friend tried it that way and ran into a ton of issues with trapped air in the system that he could not purge. Hence why he wants to just return the fuel to their respective tanks.

That said, it sounds like we could get away with just two 3-port valves.

Valve 1 is the supply valve taking 2 inputs: (from diesel tank or from WVO tank) and going to 1 output to lift pump/IP

Valve 2 is for the return fuel lines. It would have to be hooked up backwards from the way the supply valve is hooked up. One input (return fuel line from the cigar hose downstream of the spin on fuel filter) and 2 outputs to either the diesel tank or the VO tank.
One

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