7 of Mine

I am currently testing all systems before the initial start after a USDM S4 NA to JDM S5 TII swap. I find that when I run the fuel pump by jumping the test connector, the fuel pump runs and pumps fuel through the filter into a catch can, but when connected to the fuel rail, no fuel flows through the return to tank line. I understand that the lines are connected reverse on a JDM from USDM. I have the high pressure line from the fuel filter connected to the rear fuel "inlet", which feeds the fuel pressure regulator, then through the fuel rail and return through the front "return" hose. Does the FPR require vacuum to allow fuel to flow or could I have a problem or blockage inthe FPR/fuel rail?

BTW, I have scoured this site for months and found hundreds of answers to my wiring and mechanical S4-S5 conversion questions - this is an incredible resource - Thanks!

RotaryRocket88

iTrader: (7)

This is backwards. The FPR is always last in line to see fuel. The order should be:

Fuel filter -> Rails -> FPR -> Return

7 of Mine

Thanks for the help 88.
What is meant (in this forum) when they say the fuel lines on a JDM are reversed from a USDM? I assumed (incorrectly!) that meant going through the FPR first even though that did not make mechanical sense.
The correct fuel path should enter through the pulsation dampener and exit through the FPR - that should fix the problem...Thanks.

RotaryRocket88

iTrader: (7)

US-spec cars have the PD on the primary rail & the FPR on the secondary rail. J-spec cars are the opposite: FPR on the primary & PD on the secondary. The metal hardlines are a little different, but you essentially flip where you connect the feed & return lines.

7 of Mine

Got It! Just what I needed to know...On to the next step!