John V

iTrader: (1)

Yeah when I studied it on the bench it looked like it would still flow through the siphon with the regulator plug in place. It definitely doesn't backflow fuel to the passenger's side but it doesn't draw fuel to the driver's side either, at least not very much. I got the tiniest vacuum on a gauge I put on the suction line in the passenger's side of the tank with the pump running, not enough to move any usable volume of fuel, though.

Adax

iTrader: (2)

I disassembled my spare Series II pump and honestly can't quite figure out the plumbing either. I'll post back if my unconventional setup starts to fail me but I think it makes sense. I'll look into a float valve to allow surge tank air purge without fuel flow.

TeamRX8

iTrader: (25)

The question is this; is the small black hose line under pressure or vacuum? If the siphon is integral to the same module high pressure filter assembly then the black hose must be under vacuum and the only way the siphon can work is for flow to go through the bypass valve. Which if that’s plugged then there’s no way for the siphon to work.

If the small black hose is intended for pressure then the siphon must be the first appendage at the small inner cup that the module siphon hose connection feeds into. If that’s the case then the siphon would theoretically continue to work with the bypass plugged. However, it might be affected by how much pressure it receives. If the external regulator is dropping the pressure too much then it might result in the siphon not working properly.

I’m inclined to think the siphon is before the small black hose and it’s pulling a vacuum rather than pressure, but I can’t say that with 100% certainty. The way the two black hose lines come together at the inner siphon cup suggest that the flow direction is biased towards drawing fuel in vacuum rather than flowing in the other direction.

Doesn’t really matter much for me since the recent discussions have convinced me to stick with the basic OE setup, but with some critical configuration improvements to meet my overall goal on how the car is setup. I don’t need any more flow than the S2 module can do with a 265 LPH pump on E85 fuel for an NA engine and I don’t need it to run bone dry; though I think it will. Don’t want to be accused of going full pedantic again, so keeping those details to myself.

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