I am using the sfmu with stock injectors on 7 psi. i do not have the vac restrictor in the vac line for the sfmu. I am using the dark spring and largets disk, my idle fuel pressure is about 48, and when i go into boost my fuel pressure won't go over 70 psi, and it starts to run lean. I wa sthinkin about runnin the walbro 255 and a msd inline pump. Any suggestions??? I need to fix this damn thing!!

Thanks in advance

could be a fuel pump issue. Do you already have the walbro or do you just have an inline or what? I was a little confused by your post.

You obviously have a way to view fuel pressure under boost, but here's a little tip when trouble shooting your problem: you can use a small air compressor to fool the sfmu into seeing boost to determine whether or not your fuel pressure is rising to where it needs to be for your boost level without putting the motor in danger by actually boosting.

hey slammed having some problems?
I assume the ms never got sent out yet since your car isn't running.

Did you adjust anything on the sfmu once you got it from me?
I had it set good and I ran 8psi. At idle it was around 50 or so if I remember. Once in boost, the fuel pressure would keep rising. Pretty sure it passed 70psi.
I did have a walbro 255 installed prior, but was running stock injectors. If you have a stock fuel pump, this could be your problem.
Hopefully you figure this out so I can get my ms.
Downtime sucks.

Originally posted by vroom-vroom
If you have a stock fuel pump, this could be your problem.

If you have a stock fuel pump, this IS your problem

Yes the walbro is installed and it still won't rise over 70. Don't know why. I'm gonna try to add the inline pump to the walbro and see what happens.

Ohhhh. and vroom, your parts have been sent.

Good stuff got your pm. Let us know the outcome. Always good for others to read so we don't have 5 million threads about sfmu's.

+1 vroom vroom

I fixed the problem. Adding the inline pump to the Walbr 255 worked great, i still need to play with my idle fuel pressures, because with 2 pumps, there is a larger volume of fuel in the rail. This could be a good to possibly squeeze a couple more psi out of the stock injectors. Accel 32lbs on the way. lol

So today i got the lean issue fixed. I did get some Accel 32 lb. Injectors, and put them in. Now my fuel setup is...

Walbro 255 in tank( I think it is going bad. lol)
MSD Inline pump on firewall
Accel 32 Lb injectors.
S-FMU

I am using the biggest disk and dark spring,
Running a 22 psi iddle fuel pressure,
Idle slightly rich-13.6 afr

Under 5 psi boost@85psi fp with 11.8 afr.

I am very happy....for now.

congrats