Well, I have come to the conclusion that there is something wrong with my Begi 2025 FMU. It seems that no matter how I adjust the needle valve on the FMU, my fuel pressure still goes from 48 at idle to 75 at WOT. I can't tell for sure during driving because I only have a gauge tapped on my fuel rail. I'm not sure if I can accurately tell by this, but when I crack the throttle while looking at the gauge, it jumps from 48 to 75 like I said before. And no matter how I adjust the needle valve, it always hits 75 psi. Any ideas? The FMU is brand new, so I'm kind of baffled.
Right now I have the GM S/C on my 2.4L with the stock pulley. I have the needle valve all the way out, and my exhaust is still a cloud of black smoke and smells kinda like gas.
Also, I plan on putting in a new motor and getting a smaller pulley, alky injection, etc. Assuming I get the FMU working correctly, can I get my car tuned at any Dyno shop? I mean will they actually tune the FMU so I have a good A/F ratio? And do I have to have a wideband, or can they do it without one?
2010 Subaru Impreza WRX Limited
1999 Cavalier Z24 Supercharged
1999 Grand AM SE (Beater Car)
1997 GMC Sierra
2007 Honda CBR 600RR
2005 Honda TRX450R
lower your base pressure and atmospheric that could also be why...
LE61T PTE6262 Powered 
stock fuel pump? you have it set way steep or you have your one way valve on backwards, remove it for tuning..... should be able to blow out from the FMU.
HP Tuners | Garrett T3/T04B | 2.5" Charge Pipes | 2.5" Downpipe | 650 Injectors | HO Manifold | Addco front/rear | Motor Mounts | HKS SSQV | Spec stage 3 | AEM UEGO Wideband | Team Green LSD | FMIC | 2.3 cams | 2.3 oil pump swap | 280WHP | Now ECOTECED
I tried lowering the base pressure some, but then it doesn't like to idle.
Yes, I've got the stock pump yet. And no, I don't have it set too steep. That was the point of this post. I have the needle valve ALL the way out, which is supposed raise the pressure the least. What do you mean by the one way valve on backwards?? I never had to install any type of valve....
2010 Subaru Impreza WRX Limited
1999 Cavalier Z24 Supercharged
1999 Grand AM SE (Beater Car)
1997 GMC Sierra
2007 Honda CBR 600RR
2005 Honda TRX450R
The FMU should have came with a little black & white check valve that goes on the vacuum line that comes off the needle valve.
The black part should face open air.
http://www.bellengineering.net/Pages/products_FPR_Instruction.html
IIRC the newer ones don't come with the valve, but if you don't have one, then that is not your probleem, lol
HP Tuners | Garrett T3/T04B | 2.5" Charge Pipes | 2.5" Downpipe | 650 Injectors | HO Manifold | Addco front/rear | Motor Mounts | HKS SSQV | Spec stage 3 | AEM UEGO Wideband | Team Green LSD | FMIC | 2.3 cams | 2.3 oil pump swap | 280WHP | Now ECOTECED
there is a3 thousandths shim in the lower half of the diaphram. this can sometimes become damaged when you over adjust the fmu (turn the srew too far down). you need to open the fmu up and replace the shim (its about 1.5" square piece) you should be able to get it from a hardware store.
supporting post
^^^^Awesome! Thanks for that link and pic. I'm going to take apart the FMU tomorrow and take a peek to see if that's the problem.
2010 Subaru Impreza WRX Limited
1999 Cavalier Z24 Supercharged
1999 Grand AM SE (Beater Car)
1997 GMC Sierra
2007 Honda CBR 600RR
2005 Honda TRX450R
so that is damaged from turning the idle adjustment screw all the way down, weird. that makes sense though. i never touched mine really, i just moved it outwards.
thanks for the heads up / easy fix for people that have this problem.
Now I have a new problem. The AFPR that I put in was defective, so I put my stock FPR back in. Now in idles at 50 PSI, which is WAY too high. My motor doesn't even run right until I get in the high RPM's. I keep throwing an engine code that I have a misfire in cylinder # 1. I turned the big screw on the FMU, and it will raise the base pressure, but not lower it.
I've got a Walbro 255 also if that has anything to do with it. My only other idea to fix this is to eliminate the stock FPR and let the FMU manage the base pressure. Any ideas???
Also, wheither this is related or not my stock FPR went out the other day. Gas was spraying out the vacuum line and into the TB, filling up my supercharger. I put the new FPR on and it works, but it is still idling at 50 PSI.
2010 Subaru Impreza WRX Limited
1999 Cavalier Z24 Supercharged
1999 Grand AM SE (Beater Car)
1997 GMC Sierra
2007 Honda CBR 600RR
2005 Honda TRX450R
do you have the vacuum line attached to the FPR? (seems like you do, since you said your first stock one was leaking fuel into the S/C) It should idle at about 40-43psi with vacuum...... and 50-53psi w/o...... Bypass the FMU for now, just to check the FPR base pressure, the FMU will only go as low as the base pressure of the FPR.
or just ditch the FMU, get some injectors and 2bar MAP, and stop on down for some HPT fun
SPD RCR Z -
'02 Z24 420whp
SLO GOAT -
'04 GTO 305whp
W41 BOI -
'78 Buick Opel Isuzu W41 Swap
Yes, vacuum line is attached. ANd when I detach it, fuel pressure goes up by about 10 psi.
I would LOVE to do that! I've already got a 2 bar MAP sitting on my spare motor and I have the S/C injectors in my car now. When are you available?!
2010 Subaru Impreza WRX Limited
1999 Cavalier Z24 Supercharged
1999 Grand AM SE (Beater Car)
1997 GMC Sierra
2007 Honda CBR 600RR
2005 Honda TRX450R
