losing fuel pressure on acceleration. lean at wot

[entrapm3nt]

So recently I reset ignition timing and fixed a idle issue. Since then it is running lean during wot. It goes to around 11 or 12 at first but then goes to 13-14. I always let off if I see it leaning. I checked my aeromotive fpr and when I hit the gas at idle it looses about 5psi fuel pressure. I have a walbro 255 already. A brand new tt z32 fuel filter. Is it possible my fuel pump is faulty or just not good enough? The pump isn't old. My fuel pressure is set pretty high at 50psi. For my set up it might not even be high enough.I know stock is much lower. I'm only boosting 10 lbs atm. I want to turn it up but need to fix this issue. Even with only 10 lbs it feels slow to me. No vac or boost leaks. 165 compression across. Here's a list of mods I have.

sr20det
RS-Empathy rom ecu
mazworx timing chain tensioner
tomei 270/270 pro camshafts
tomei headgasket
tomei rocker arm stoppers
brian crower bc valve springs / retainers
arp headstuds
arp main studs
bored .020 over
wiseco .86.5mm 8:8:1 pistons
eagle rods
greddy oil pan
greddy oil filter relocation kit
greddy front mount intercooler kit
greddy intake manifold
hks ssqv blowoff valve
1000cc five-O injectors
aeromotive fuel pressure regulator
garret GT2871r .86 hotside turbo
Z32 isis mass air flow sensor
isis air intake kit
Z32 fuel filter
Walbro 255 fuel pump

going to test the pump in the next few days but just wanted to see what you guys think.

[derass]

The fuel pressure dropping when you rev the engine from idle is wrong. It should increase. I would start there.

[entrapm3nt]

The fuel pressure dropping when you rev the engine from idle is wrong. It should increase. I would start there.

Yes it should increase. My vacuum is a little low as well but it does have big ass cams. It's around -16inhg.

edit: could it be anything else besides the filter or pump? Lines look fine. If they were kinked it would be high pressure.

[derass]

In some cases, the fuel pump not delivering enough volume could explain what you're describing. However, I don't think that's the case for you at only 10 psi. If it was 20, than maybe.

You should verify that you are actually loosing fuel pressure. Tape a pressure gauge to the wiper blade and go for a drive.

My car would keep reading lean and I couldn't figure out why. Ended up being a faulty 02 sensor. You can try this test: https://www.youtube.com/watch?v=onbjzEOZtMs

[entrapm3nt]

In some cases, the fuel pump not delivering enough volume could explain what you're describing. However, I don't think that's the case for you at only 10 psi. If it was 20, than maybe.

You should verify that you are actually loosing fuel pressure. Tape a pressure gauge to the wiper blade and go for a drive.

My car would keep reading lean and I couldn't figure out why. Ended up being a faulty 02 sensor. You can try this test: https://www.youtube.com/watch?v=onbjzEOZtMs

Thanks for the link. I'll try that. I have not tested it while driving but there is a gauge on my fpr and shows its losing pressure when I hit the gas at idle. With it leaning I just asumed it was also under load I'll confirm that later tho.

[derass]

Try taking the vacuum hose off the FPR and revving it. I have a feeling the problem has something to do with the FRP.

Many people with these cars rewire the fuel pump, but I don't think you have to do that just yet. You shouldn't be losing fuel pressure just by revving it a little bit.

[entrapm3nt]

Try taking the vacuum hose off the FPR and revving it. I have a feeling the problem has something to do with the FRP.

Many people with these cars also rewire the fuel pump, but you shouldn't be losing fuel pressure just by revving it a little bit.

What should it do with vac unplugged revving it? The fpr is brand new and aeromotive.

[KAT-PWR]

Well...
Do you have the fuel pump wired via a relay so it receives pure 12V+ power at all times when the key is on? Or is it running through the 20+ year old crusty corroded wire and not likely supplying adequate voltage?
That's where I'd put my money. Unless you bought an eBay Walbro and got hosed by one of the many eBay vendors selling cheap pumps as legit walbros. (Very common)
Your fuel pressure should be factory regardless of your "setup" as that is what just about every injector is tested and meant for (3 bar fuel pressure) unless you happen to be running 4 bar pressure which is very unlikely.

[derass]

What should it do with vac unplugged revving it? The fpr is brand new and aeromotive.

I'm thinking it will drop less, if at all. Maybe I'm wrong, but it's a quick check to see if the FPR is the culprit.

[entrapm3nt]

Well...
Do you have the fuel pump wired via a relay so it receives pure 12V+ power at all times when the key is on? Or is it running through the 20+ year old crusty corroded wire and not likely supplying adequate voltage?

No relay. Pretty sure it's always on with the key. I have not tested voltage yet.

[entrapm3nt]

I'm thinking it will drop less, if at all. Maybe I'm wrong, but it's a quick check to see if the FPR is the culprit.

So if it doesn't drop that would mean my fpr is bad? I highly doubt it is but I'll Def test it as soon as I can. Thanks for all info so far guys. I'll try to keep you posted in case other have similar problems.

[KAT-PWR]

The number one thing you should do when doing anything passed stock KA is a direct wire fuel pump.

[derass]

Maybe not bad, but not connect properly. Maybe the send and return lines are mixed up or the vacuum line is connected to the wrong port on the engine. Is it an S13 or S14/15 SR?

[entrapm3nt]

Kat you said my fpr should be set at stock pressure regardless of my modifications? I've never herd that before. Then what would be the point in having a fpr besides the gauge?

[entrapm3nt]

Maybe not bad, but not connect properly. Maybe the send and return lines are mixed up or the vacuum line is connected to the wrong port on the engine. Is it an S13 or S14/15 SR?

Positive everything is hooked up corrently. It's a s13 sr into a S14 kouki using wiring specalites harness

[KAT-PWR]

Kat you said my fpr should be set at stock pressure regardless of my modifications? I've never herd that before. Then what would be the point in having a fpr besides the gauge?

It offers precise control over more powerful pumps.

[entrapm3nt]

The number one thing you should do when doing anything passed stock KA is a direct wire fuel pump.

That's what I ment. Hard wired. It's a sr btw. And you mentioned injectors. I have 1000cc. I don't think stock fuel pressure is enough it actually runs terrible with it that low.

[derass]

Kat you said my fpr should be set at stock pressure regardless of my modifications? I've never herd that before. Then what would be the point in having a fpr besides the gauge?

I agree. It should be stock pressure. One reason for changing to an adjustable FPR is because the stock one can't bypass enough with an upgraded pump and the car ends up running a little rich, but it's nothing major.

Positive everything is hooked up corrently. It's a s13 sr into a S14 kouki using wiring specalites harness

The vacuum hose should be going to one of the top two vacuum ports on the throttle body.


I disagree that the pump always has to be rewired. I've been using a Walboro with the stock wiring for 5+ years now and haven't had an issue. However, some cars may have worse wiring than others. IIRC, the connector is packed with grease to prevent corrosion.

[KAT-PWR]

How do you have the pump direct wired without a relay?. Injectors are all rated at standard pressures (3bar/3.5bar/4bar)
I just looked up five-o 1000cc injectors. Looks like they only flow 750cc at 3bar. Their information is a little confusing from what I can see. I'm guessing five0 is wanting these run at 4bar for 1000cc flow.

EDIT: Upon further looking it really seems like they're wanting high pressure to get these to act as 1000cc injectors, which probably explains it. If you look at other injectors like Injector Dynamics their 1000cc injectors flow a true 1000cc at 3bar pressure, same for most others.

[entrapm3nt]

How do you have the pump direct wired without a relay?. Injectors are all rated at standard pressures (3bar/3.5bar/4bar)
I just looked up five-o 1000cc injectors. Looks like they only flow 750cc at 3bar. Their information is a little confusing from what I can see. I'm guessing five0 is wanting these run at 4bar for 1000cc flow.

I don't remember seeing a relay. So having my fpr higher would be normal then? I'm starting to think maybe a bad pump or it can't keep up. It was installed when I got the car but was told it was new. Obviously I need to check over this again on my next day off.

[KAT-PWR]

I'd start with the relay. Some people don't have problems, but enough do that Martin advises everyone to do it. (At least that I know)
Then I'd call five0 and ask what the deal is, and set the pressure according to what they say.

[derass]

It should be able to keep up when idling and revving. It would have to be nearly dead otherwise.

Is your pump wiring stock or has it been modified? I'm unclear about that.