Return line through fill tube

[pierre71]

I may need to redo my return line and was considering this possibility as it says in the MS manual. Putting a bug into the fill tube, then bend some metal line, run it through the trunk floor (my fill tube runs from quarter panel, through trunk floor, to tank) then from under the car back to under the hood and regulator.

The only thing I'm worried about is if the pressure on the return side is enough to push the fuel up a vertical stretch, turn 180 degrees, and dump into the fill tube from the top. I'd rather do it from the top of fill tube because if the joint does crack it will be less likely to leak into the trunk.

I'm running a walbro gsl392 pump, 5/16" pickup line, and 5/16" return line. The fuel rail has 1/4" output for the return but I adapted this back to 5/16" to match everything else, so I suppose ultimately the return line can be called 1/4"

[PSIG]

Your plan sounds possible if done carefully. The vertical rise is no issue as it requires less than ½ psi to push fuel vertical per foot. If it is not possible to avoid passing through the trunk, be sure to protect the lines and fittings from impact and abrasion damage.