OK before I get to my question, let me tell you about my setup, I am running an HRC S16G Stage 2 with stock injectors (for now) and the SFMU with the largest disk and dark spring. I just switched from my stock fuel pump with an msd pump for boost to just a walbro 255lph HP. Installation went ok however when I first turned it on, the idle FP was at 55psi. A little too much for what I wanted to be at so I tried to bring back down to between 47-50psi but when I turned the static screw on top of the SFMU and guess what, the pressure did not change. Now just to make sure, I checked all the hoses and clamps and there are no fuel leaks any where. I even tried tighten it all the way and loosening it back up but the FP stays the same no matter what I did. Now when I boost @ 6psi, the FP goes to around 80 which was the same as when I had the 2 pumps going. I guess my real concern/question is, why would the SFMU not read an FP changes when adjusting the static screw at idle???

http://www.cardomain.com/id/hunntyr


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check the diaphragm

What year is your car?

If your fuel return to the tank isn't sufficient you'll be unable to lower your fuel pressure under a certain point.

Joel Baldridge, ASE Certified Master Technician, Audi Certified Expert Technician

I got my idle FP down to about 19psi on 440s so it's definitely possible to get below 50psi.

I agree, take the sfmu apart and check for tears in the diaphragms. If the FP screw gets cranked down too hard, it can go rip the diaphragm.

http://www.cardomain.com/id/hunntyr


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when fully warmed up, i run between 14-18 psi @ idle with 40#'s and the same disk you got

I am curious as I am going to be installing the same turbo setup as well as the same fuel system. Let me know how you correct it man and good luck!

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- 05 Subaru STi
- 97 eclipse gs (289whp w/ 276tq)

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98 ESi
95 GS

http://www.cardomain.com/id/hunntyr


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- Is your factory FPR disabled completely? See: http://www.2gnt.com/www/corbin/fpr.html


- Do you have the SFMU and gauge after the fuel rail?


- Evulflea: Yes, 15psi idle fuel pressure SUCKS

- IIRC there are TWO diaphragms in the SFMU. The smaller one is about 1" in diameter. It's the big one that usually rips though.

Yes, the FPR is taken care of and yes the SFMU is hooked up where the windsheild resevoir used to be.

http://www.cardomain.com/id/hunntyr


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Sounds like you have a clogged return line. If you remove the static screw with the pump running does the pressure still remain at 55psi? If so you either have a SFMU faiure or return line restriction.

Terry

http://www.cardomain.com/id/hunntyr


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i also have this problem...im also a 95...i think mine wont go lower than 40ish?? i was planning on running a bigger return line, just dont know how big to go....what do you 96 and up guys run...
doug

14b custom turbo kit, modified starion front mount, 9.6:1 JE pistons/Eagle rods....running 12psi
screw flanders

Well I have a 95 and I can go as low as like 8-10 psi of static fuel pressure, car will sputter when I do that. My fuel lines are bone stock.

Kevin
The old:


The new:

Somthign has to be restricting the pressure release. since it still rises it sounds like the return line. are you sure you dont have a kiked line by the tank? In my 96 i use the OEM feed line as my return line. By any chance did you change the fittings in the SFMU? the fittings are 6an unions with o-rings (one end has the male flare removed). If you changed the fitting and didnt remove the flare, perhaps it is close to bottoming out and restricting the fuel flow. Maybe use a air hose to bow out your return line and make sure that isnt something in the line other than fuel.

Terry

Well, it turned out to be a clogged line so I am ok on that aspect. My final question for this is, I just got in my 330cc's. Now I am using the largest disk in my SFMU and the dark spring however I am not 100% sure which disk setup to use for the larger injectors. From what I read it was the 2.72 ( the next smallest down from Largest disk) with the dark spring. Can anyone confirm this??

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I think that you will need to datalog or check your A/f ratio to be exact. the 272 disk is used with the 440cc injectors most of the time. It makes sense to try it with the 330's just make sure you have a wideband or a decent little narrow band display to watch the A/f ratio just in case.

Good to see you found the problem.