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Discussion Starter #1
Hoping i can get some help/advise/insight from you guys.

Decided to rebuild the engine after a rod knock in my 15STI, now I m having an issue with high fuel pressure (58 PSI), idle gets bouncy after it is warm up. It is impossible to drive it without stalling all the time. The ECU has been flashed with a new basemap from a local tuner, assuming it was done correctly based on my mods.

At idle, the FP reads 58psi. The fuel sensor was installed on the FPR on the return line before the ethanol sensor. But when the supply line gets pinched the pressure can drop down to 42psi, idle will stable, and the WB 450 pump inside the surge tanks whines.

The radium surge tank has 4x -6 line connections, WB450 hardwired to the battery. Also a hard wire kit tapping the relay to the fuel pressure controller in the trunk.

BOV is tight shut at idle, no sign of vacuum leak.


Build:

Dom XT 1.5
1700 CC injectors
TGV deletes
Killerbee ELH
Killerbee oil pan and pickup
3 inch inlet
New built motor with forged internals
Cobb AOS

Cobb Flex fuel kit with fuel pressure sensor
Aeromotive Fuel Pressure regulator

Radium surge tank with WB 450
Aeromotive 325 in stock tank
Stock fuel rails

Any help will be appreciated.

Thanks.
 

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Discussion Starter #4
Adjust the fuel pressure regulator. If that doesn't work, warranty it.
the adjustable FPR is already maxed out.

It might be back pressure created in the return line in the oem fuel pump hangar. I was told that the venturi becomes a restriction in the oem tank, and should get a Radium fuel pump hangar.
 

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Discussion Starter #5
This.

Your aftermarket FPR needs to be adjusted to the pressure your tuner wants.
My tuner said that it is mechanical when the base pressure is out of spec, should be corrected first. He doesn't tune around mechanical issues.
 

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the adjustable FPR is already maxed out.



It might be back pressure created in the return line in the oem fuel pump hangar. I was told that the venturi becomes a restriction in the oem tank, and should get a Radium fuel pump hangar.


What kind of fuel pressure are you looking for? It shouldn’t be maxed out if you need to lower it?!

I have the same FPR as you, and I was able to set my idle fuel pressure perfectly with plenty of adjustment still available. You don’t want your idle fuel pressure to be 60psi, that would put your WOT fp around 80-90psi...(depending on your boost level)
 

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I have a bigger jet pump, but prior to installing that, I ran the stock one without issue. That said, I have a 2005 and the hangar is different.

Are you saying you cannot go any lower on pressure when you back it off with the regulator? I wouldn't expect any decent tuner to tune around this. We are going off whatever little information you provided. If you disconnect the feed pump in the tank, does it allow you to bring the pressure down with just the surge tank using what's in the tank (and its return back into the surge tank)?

Be sure you are setting base pressure without vacuum or boost.
 

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Discussion Starter #9
What kind of fuel pressure are you looking for? It shouldn’t be maxed out if you need to lower it?!

I have the same FPR as you, and I was able to set my idle fuel pressure perfectly with plenty of adjustment still available. You don’t want your idle fuel pressure to be 60psi, that would put your WOT fp around 80-90psi...(depending on your boost level)
The idle pressure needs to be at around 42ish psi, but it is at 58+ psi. The Aeromotive FPR can't lower it anymore.

The static pressure with just the wb 450 pump in the surge tank running at 100% is at 42 psi.

Suspecting that it is back pressure coming from the OEM fuel pump hangar. Radium told me that it is because of the increasing fuel-flow, the venturi becomes a restriction, rendering the regulator useless.

"One solution is to use our fuel pump hanger for your vehicle. This gives multiple pump options, as well as incorporating our high flow venturi. This will operate at high fuel flow rates and still retain OEM functionality of the fuel tank."
 

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If you turn off the pump in the tank, the surge tank will eliminate the factory hanger situation. If you cannot lower the base pressure when you disconnect power to the in-tank pump, your regulator is bad.
 

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Listen to Noximous. Remove the vacuum line and start from there. Sounds like your tuner doesn't know jack shit and you should be looking for a new one
 

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The idle pressure needs to be at around 42ish psi, but it is at 58+ psi. The Aeromotive FPR can't lower it anymore.

As we’ve been eluding to, but you haven’t answered on it yet, are those numbers with the vacuum line disconnected from the FPR? Base idle pressure needs to be set with the vacuum line disconnected.
 

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Discussion Starter #13
If you turn off the pump in the tank, the surge tank will eliminate the factory hanger situation. If you cannot lower the base pressure when you disconnect power to the in-tank pump, your regulator is bad.
Just want to clarify. Do i unplug the harness on the oem fuel pump, turn on the power (not starting up), then adjust the FPR to see if it will get lower the base pressure? Thanks.
 

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Discussion Starter #14
As we’ve been eluding to, but you haven’t answered on it yet, are those numbers with the vacuum line disconnected from the FPR? Base idle pressure needs to be set with the vacuum line disconnected.
The line was connected still. Do i need to plug the port on the FPR or the vacuum line if i disconnect it? thanks.
 

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You can pull the power on the in-tank pump before or after starting.

Although you set base pressure with no boost or vacuum, if you could not get it lower with vacuum, you're not going to lower it just by pulling the reference hose. Vacuum is supposed to bring pressure down even more.

If you just jump the pump in the surge tank on without starting the car, you can set pressure without removing the power to the in-tank pumps and without removing the reference line. This also eliminates the factory hanger.
 

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Discussion Starter #17
As we’ve been eluding to, but you haven’t answered on it yet, are those numbers with the vacuum line disconnected from the FPR? Base idle pressure needs to be set with the vacuum line disconnected.
The fuel pressure is the same at 58 psi with the vacuum line disconnected from the FPR.

Should i try to adjust the FPR with the vacuum line disconnected? thanks.
 

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Discussion Starter #19
Problem solved. Got an advice from Radium, it was probably the jet pump in the OEM fuel hangar was too restrictive, creating back pressure.

So I installed a Radium fuel hangar with a WB 450, the pressure came back down, still has room for adjustment with the FPR.

Thanks everyone for your advice.
 
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