I still CANNOT get over 80 psi of FP when boosting 7 -8 psi. I pulled the plugs yesterday (brand new bkr7e's @ .031) and the first cylinder is just barely white.

I have the largest disc/no ring/dark spring/stock injectors combo in and I'm getting annoyed. I have 47psi at idle which is great but it only seems to raise to 80 which is only 4.7 psi raise in pressure per psi of boost.

I don't want to bag on the car till this is figured out and I recieve my techedge and EGT gauge But I'd like to be able to drive is fairly lively :P :P

My return line from the sfmu is stock, diapragm is new, sfmu is installed correctly. boost screw is in, vacume screw is out about 2 turns. Grrr.

I don't know what to do about the vacume screw. It seemed that before, It was screwed all the way in and it wouoldn't even reach 80 psi. I then backed it out a bit and got to the 80 but now unscrewing it more doesn't yield any diff. results.

And yes I've searched. I'ev read EVERY SFMU post possible. My eyes are bleeding.

Owww.

come on peeps.

I know this topic is getting old.

That sounds definately like a fuel pump issue. I take it it's of course upgraded over stock, probably a wal-bro 255. The pump may be going bad, the voltage might not be high enough (re-wire it like me), the MFI relay could be bad. You could also have a bad/clogged fuel filter, change that too.

you got a good vac signal to your SFMU?

Originally posted by micyek
you got a good vac signal to your SFMU?

Of course. Right off the back of the manifold. Nothing is tee'd off it or anything.

Originally posted by Blizare
Of course. Right off the back of the manifold. Nothing is tee'd off it or anything.

well neenee neenee...look at me my name is Blair I'm so smart :P

Idunno...I just thought I would ask the simple question first...

Originally posted by micyek
well neenee neenee...look at me my name is Blair I'm so smart :P

Hahaha :order

Originally posted by WickedESi
That sounds definately like a fuel pump issue. I take it it's of course upgraded over stock, probably a wal-bro 255. The pump may be going bad, the voltage might not be high enough (re-wire it like me), the MFI relay could be bad. You could also have a bad/clogged fuel filter, change that too.

Okay. Now thats some help :p

I do have a new walbro 255 in the tank. I had a problem at the track this weekend and ended up running a straight 12V from the battery on a switch because the fuel pump relay went on me. So you think I should change the MFI relay also??

I should also check my fuel filter. I haven't in a couple years :P

Thanks wickedesi....you too Kent :P

Yeah, I would get those relays switched out and that fuel filter ASAP. If that alone doesn't let you build over 100 psi, do the pump rewire "mod".

Originally posted by Blizare
I should also check my fuel filter. I haven't in a couple years :P

I am going to have to throw up a flag on this one.... I bet a used zebra cake in mint condition that its the fuel filter.

Okay, got the fuel filter changed.....No difference in FP. I didn't change the relays but did rewire the fuel pump and still no change.

Does anyone's walbro have the normal "Hummmmmmmm" noise but then they step on the gas and then it goes away.......did that make sense?

my Walbro sounds like a dentist tool does at low rpm while priming... if that makes any sense. While driving, it sounds like a dentist tool at high rpm, and under throttle it sounds just like it does at idle... since if I remember right, your fp is always outputting the same pressure no matter what kind of driving you are doing.

At low RPM it has to FLOW a lot when the fuel pressure is low (because nothing is restricting the circuit, the pump is flowing at full blast), and that's why it's the loudest when there is no load.

Originally posted by WickedESi
At low RPM it has to FLOW a lot when the fuel pressure is low (because nothing is restricting the circuit, the pump is flowing at full blast), and that's why it's the loudest when there is no load.

ahh alright that makes more sense, I always get that whole hose-spigot-more volume explanation mixed up.

Originally posted by WickedESi
At low RPM it has to FLOW a lot when the fuel pressure is low (because nothing is restricting the circuit, the pump is flowing at full blast), and that's why it's the loudest when there is no load.

Okay so when there is a load it is normal to quiet down some?

That would mean the fuel pump is fine then.

I don't know what the problem is then. I don't think the relays are restricting the flow of fuel.

Fuck sakes. :shrug

maybe your injectors are shot? idk i'm definetly not the expert, but just throwin stuff out there since you seem very stumped. Good luck figuring it out