FPR and boost gauge issues

[nuclearpenguin]

Before I ever did my head swap, my boost gauge occasionally wouldn't work at all until a couple minutes after starting the car. Looking back, I know this is most likely because it was hooked up on the wrong side of the FPR solenoid, common problem, easy solution (now that I've stumbled upon it, read on however!). After doing the head swap, now I have an issue where it only shows boost on occasion. Usually within the first 3-5 minutes of starting the motor. I've ALSO noticed that when it does go into boost on these occasions, it never feels very powerful. My car has felt very sluggish almost since I got it. I mean there's times when I really feel the power, and other times when I don't.

Today is when I finally realized that the boost gauge was hooked up on the wrong side of the solenoid so I fixed it. I'm wondering though is there a correlation between the boost gauge woes and my sluggishness problem? Maybe a faulty FPR would cause the boost gauge to act that way? I'm not very well versed on how the FPR works. I have been thinking my sluggishness problem is related to the ignition system, but as I'm looking at my logs, it is looking more and more like a fuel issue. I have insane amounts of knock...sometimes. (and I don't think it's PK because I have 3g lifters and don't know what else would cause that much PK, sometimes I have 1 count of knock, sometimes I have 43; sometimes both in the same log!!). My o2vs seemed to always be around .92v but I noticed logging the other night they were at .88v. I have my S-AFC set to +5% because I hacked my 1g MAF. Other than that my profile is entirely up to date. So here's what I'm looking to know:

How exactly does the FPR work with the FP solenoid? When is there vacuum in that line? Could a faulty fpr cause it to always show vacuum when it should, but rarely boost? Would a fpr acting in this manner cause a lean (or maybe really rich) condition?

Please help wisemen! My car got beat by a Honda, I know something's really really wrong!

 

[DGajre777]

The stock FPR increases fuel pressure on a 1:1 ratio to boost. This means that for every 1 psi of boost the fuel pressure increases by 1psi. On a 2G your base fuel pressure (with the port nipple disconnected) is 43 psi (37psi on 1Gs).

Now, if you are at 0 boost, it is 37 psi on the 1G.
If you are at 10 psi of boost, your fuel pressure will be 47 psi on the 1G
20 psi of boost = 57psi fuel pressure on the 1G.

The FP solenoid is tapped into the FPR. You tap this line and connect it to your boost gauge. There is vacuum in that line when you are not building boost. Make sure your hoses are good and secured too. If you are boosting at 20 psi and the FPR solenoid hose comes off while your fuel pressure is at 57 psi (on the 1G), your fuel pressure automatically drops to 37 psi (NOT GOOD!).

While you are at it, do a boost leak test too, you might have a leak somewhere in your intake after the MAS.

 

[scottsee]

^^ what he said.

 

[nuclearpenguin]

i test drove it tonight after replacing my coil pack and power transistor and hooking my boost gauge back up the right way. it read boost for the whole ride, but the car was sluggish for the whole ride. i mean, if i went into boost, it felt like crap! i got on it and logged one pass, injector dutys went to 117%!! at only 10psi! any ideas what i should check?

 

[nuclearpenguin]

Ok, I was thinkin about this... and based on what I've learned in this thread and seen from my gauge, my FP solenoid must be bad. Since I was only rarely seeing boost on the line between the solenoid and the FPR, my FPR wasn't raising the rate during boost and that must be leaning me out. Am I right? If so, I'll just skip the solenoid and run the vacuum hose straight from the IM to the FPR...

 

[DGajre777]

Test your solenoid... a bad Fuel pressure control solenoid normally give you problems during warm start. Test the resistance across the terminals, it should read between 36-46 ohms.

If the solenoid checks out okay, you could possibly have a bad fuel pressure regulator that is no longer working or raising fuel pressure on a 1:1 ratio to boost.

Have you done a boost leak test yet?

 

[nuclearpenguin]

Test your solenoid... a bad Fuel pressure control solenoid normally give you problems during warm start. Test the resistance across the terminals, it should read between 36-46 ohms.

If the solenoid checks out okay, you could possibly have a bad fuel pressure regulator that is no longer working or raising fuel pressure on a 1:1 ratio to boost.

Have you done a boost leak test yet?

ive done them several times before (recently) and all the standard boost leaking seals are new (injector o-rings/insulators, TB gaskets, IM gasket, TB shaft seals). ill do another boost leak test tomorrow for good measure though

ill test my FP solenoid tomorrow, and ill try hooking the fpr straight to the IM just for kicks and giggles and see how it runs