Originally posted by JJW-ND
Just plumb the axillary to gravity flow into your main tank via the vent line on the fuel filler hose. No need for any filters or pumps. This has worked for half a dozen trucks we have. I have run over 8,000 gallons through mine.
We have our tanks (custom made) designed so the fuel is intake is pulling fuel directly off the bottom (90 degree elbow pointed down within 1/2" of the bottom).
With no pump you will never overflow your main tank. The flow is not fast but enough to keep up with 9 mpg (tested many times). No problems with fuel flow even in winter cold.
Put a ball valve right after the fuel leaves the axialllary tank. We add a solinoid valve downstream to allow flowing fuel on the fly with a switch in the cab.
jjw
ND