i think i may be on to something here biggie...im trying to post a video but it says its 90mb and cant figure out how to post this thing...i think it may be a vaccum line issue...the vacuum line going to the fpr is teed off to what i think is the boost gauge...but i believe its coming from some sort of valve or sensor looking thing thats on the manifold...isnt the fpr supposed to have its own vacuum source direct from the actual manifold? if i can find a picture of how others have the vacuum line to the fpr and where its coming from that would help...also where are you guys running the boost gauge to? ill keep trying to post this video, i want you to see it...

 

Thats pretty normal. People usually Tee into that vacuum line for the boost gauge. I was actually going to recommend you remove it and run the line straight to the solenoid to see if it helped. I just didn't want to throw too much out there at once. I have had many boost gauges go bad on me and you never know it could be causing some kind of an issue. I basically gave up on mechanical boost gauges and just rely on the MAP readings in my logs to monitor boost. The solenoid that the regulator runs to is there to interrupt the vacuum signal during cranking, so that you get more fuel pressure during start up.

 

Ah that makes sense...damn now I'm stumped...I followed the manual that you posted and nothing...the only thing is the car idles at 40 psi and when the car turns off the needle drops straight to 30 - 32 psi and holds there...I came back after about half an hour and the pressure was still there...this is why I thought it was a vacuum issue...it's not leaking or anything...i pinched the line and I can feel pressure...idk...

 

Ok i used this site to post the video...hopefully you guys can see it...also, I have an aem fuel rail if that matters...

 

did you do step #13?

 

i didnt do it because as you saw in the video as soon as the engine shut off it went straight to 32 as if thats where its supposed to be...itll stay on the for a good 45 minutes or so before it start dropping over time...so it didnt seem to be leaking to me...if it was slowly going down id say something is leaking (injector, pump, fpr, etc)...i will try it for the hell of it tomorrow either way...

 

this could be just how im reading it, but the way i understand it, it should stay at the pressure it was at when you shut the car off. Dropping to say 32psi to me would kind of indicate that something is allowing fuel to leak down until that pressure level. Only way to know though is to do the test and see if the behavior changes. If it does the same thing no matter what you do then its probably normal. If following #13 (1)(2) or (3) causes a change though, then you have a lead to follow.

 

im going to try it either way but its weird that the needle just drops straight to 32...if it would drop gradually then id say yeah it was leaking...but ill try either way...

 

Of course it does.
Only it drops to 33 PSI and your gauge reads wrong.


The instant you switch the car off, the pump turns off as do the injectors.It's still got manifold vacuum.
Because the pump turns off, there's no more fuel flow, the regulator is no longer being "out flowed" so it's at the correct pressure.


If you added a series resistor (just for testing) to the pump, you'd slow it down and it would also read the correct pressure. Same thing......that will also prevent FPR out flowing.

 

easy way to tell would be to just unhook the regulator and shut the car off. If the pressure doesn't drop down to that 30psi then its all good (the leak down anyway). I hadn't really considered latent vacuum in the manifold causing that initial drop, but maybe.

Also lets say it is over running the regulator, I would expect that to lead to a rich condition, not a lean one that OP is seeing.

 

So unhook vacuum line from fpr and cover it with my finger and shut car off and see what it does? Also, now that you guys mention it sometimes when I start driving and come to a stop say at a light the afr will be richer than normal...when this starts to happen is when I get on it...if the fpr wasn't doing this I would be thinking about sensors like Omni 4 bar...idk...

 

There's an evo junkyard out here...got these for $40...for the price figured I'd try the fpr and solenoid...couldn't find a resistor box and that's what I really wanted...

 

You guys were right...this picture is the car off with the vacuum line disconnected...

 

Hey Biggie I help people all the time, watch this!
Your fuel pressure fluctuations are the issue period. Your regulator is set to 32~34 psi is correct. The reason it is running higher than that could be a couple things. Fuel pump relay number 3 is sticking/welding closed, or somebody has rewired the fuel pump to stay on full speed all the time. The restrictive siphon tube in the tank can't handle max flow of a 255 walbro, that's the reason for the knockdown resistor. Relay #3 bypasses the said resistor so pulling that really out is an easy test to see if it is staying on. Car will run just fine without it, but do not get into any boost with it removed. This would also explain why it's so loud, at full voltage these pumps are loud. Try pulling the relay and check fuel pressures again.

#3 relay is on the firewall right next to the fuel pump resistor just unplug. If the fuel pressure is still high then pull a wire off the resistor and see if the fuel pump still runs, if it does the resistor has been bypassed.

 

#3 relay sticking could be a possibility. Again though fuel regulator over run would cause a rich condition, not a lean one. Let me break that down, more fuel pressure means more fuel sprays out of the injector for a given Injector pulse width = richer fuel mixture. One thing we need to see to get a better idea of whats going on in the ECU are long term fuel trims.