Shinobi'sZ

Any advantage in running a little more fuel pressure? I replaced the OEM FPR with an AFPR (Southbay) thinking it would solve my stalling issue. When I setup the fuel pressure I have it priming to 50 and then drops to 40 psi while running. I know it is a little higher than normal OEM 43.5/38 psi. Is there any harm in leaving it at 40 psi running (vacuum hooked up)? Also I am installing headers soon.

My fuel pressure doesn't hold after priming. Assuming it is either a bad check valve in the original fuel pump or an aftermarket fuel pump that doesn't have a check valve. Fuel pressure always primes and runs good...just doesn't hold at the rail after it primes. I know it's not the injectors because when I installed the new Bosch injectors it did the same thing.

Reddragon88gta

When does the engine stall? What engine? I had a nagging cold start up stall after like 3 seconds but after restarting it was fine. Did this all the time and a new ECM cured it. No check engine light either and was hard to figure out.

I run my L98 at 47-48psi with vacuum line disconnected to simulate full throttle, so it’s only a few psi more than the 44 or so it had with the stock unit under the same circumstances. I toyed around with a few settings and 47 seemed best for my set up. Also that’s what Holley recommended in the instructions as well. It helped performance a bit for sure, so you can find the best setting for you and the engine. IIRC the LB9 should be ran lower than the 350 but I have heard the Bosch IIIs are leaner than factory so a little extra will help.

I also have the same issue as you with fuel pressure not holding. New injectors, FPR etc so it sounds like factory pump check valve. No issues running and it’s been like this since I got it on 2017.

GeneralDisorder

iTrader: (1)

Get it fully up to temp and set the fuel pressure such that the BLM and INT are as close to 128 as you can get them. Check idle vacuum and ensure that when you plug in the vacuum line the pressure drops by the same as the idle vacuum (20 in/Hg ~ 10 psi). If not then the regulator isn't regulating properly.

It is not necessary for the fuel pressure to hold after shut down.

In a properly functioning (stock) system, fuel pressure will be regulated to 43.5 psi without the vacuum connected. In a stock engine making 18 in/Hg of idle vacuum, the FP at idle should be 34.6 psi.

If you mess with the pressure without tuning the ECM for it, all you will do is skew the BLM and INT values - creating an unnecessary learning curve for the ECM on every startup, and limiting it's ability to compensate for other sensor drift or environmental changes.
GD

Shinobi'sZ

Here are the links that describe what was causing the stall issue intermittently at idle and the parts I replaced trying to isolate it.
https://www.thirdgen.org/forums/tech...elp-dying.html
https://www.thirdgen.org/forums/tech...gh-output.html

I would like to check the BLM and INT but I don't have a scanner or software to read them. I do have a vacuum gauge and warm idle is right around 11-12 psi it looks like. Car runs fantastic. The only reason I wish the FP would hold on the rail is that if I don't crank immediately after prime it turns over a little bit longer to get the FP up to start. I'm assuming somebody at some point changed the fuel pump out. I should pull back the carpet in the rear and see if somebody did a hack job to get to he fuel pump. I have changed out 3 fuel pumps out of my 4 Thirdgens and always dropped the tank to swap out the fuel pump. Other than that its ****.

GeneralDisorder

iTrader: (1)

You should invest the meager $ required into a cable and software to read live data. With Bosch injectors and an adjustable FPR you are essentially shooting in the dark without scan data. The ECM will simply fight everything you do to try and get what it thinks it wants and messing with fuel pressure or injectors without considering the ECM's role is a COMPLETE exercise in futility. You may as well just poke around the engine bay with a coat hanger.

Turning over longer isn't a problem. It helps further prime the oil galleries. Just leave it.

GD

Shinobi'sZ

You're right I should. As far as the injectors go, after installing the Bosch injectors and having the dying issue persist...it ended up being a bad (made in China) ignition coil. I replaced the coil and then had the intermittent stalling issue. So I then went back and reinstalled my stock injectors (Delphi) after I made sure they ohm'd out and were clean. I did that because you mentioned on my other thread that the voltages were slightly different and after reading your Bosch testing thread. They worked fine as far as I could tell but because of the stalling issue wanted to make sure it wasn't some voltage issue difference between the Delphi and the Bosch. For reference the Delphis OHMs were all 16, the Bosch were all 14.

GeneralDisorder

iTrader: (1)

The resistance of the injectors isn't a concern. Anything in the 10+ Ohm's category is considered high impedance and should work just the same assuming the ECM's driver's can handle the current load. In itself the impedance has no effect on the voltage offsets that can be quantified.

You need to ensure the BLM and INT are within the confines of acceptable. The more you make the ECM fight what it thinks is "normal" by skewing it's numbers, the more likely a stall condition could develop. BLM, INT, and IAC steps are very important for the ECM to happily control everything within it's comfort zone. The further from it's comfort zone you take it, the more likely it is to misbehave.

GD

Annihilate

iTrader: (1)

Just a heads up in case you haven't figured this out yet.

I also installed the southbay afpr and their diaphragm, it turns out in some instances their unit will bleed through and won't allow the fuel rail to hold pressure after priming. I reinstalled my original diaphragm and it solved that issue for me.

southbay08

I wish you guys would contact us when there is a problem with any of our products. Can you send that unit back? We sell them all day long so i would like to see what the problem is with the unit. Give me your address and i'll send you a return shipping label

george88gta

same here, immediately to zero psi.

Shinobi'sZ

Just to circle back on this. My original stall issue was related to my alternator (OEM) and stereo system. I found that when I disconnected the amplifier positive lead from the battery that the car would not stall. When I hooked the amp back up to the battery the problem came back. What would happen is when the car was idling at 650-700 rpms (I think that is correct) the rpms would suddenly dip and the engine would shut off, it would start back up every time, but was mainly when I had the lights, AC, and stereo on, and would drop into gear from Park to R or D, it would die. I was intermittent and when I came up to a light and was still in D waiting for the signal to change very rarely it would happen also...but not as bad as when dropping into gear. I replaced with a Powermaster 170 amp and the problem never came back...no matter what load is on it.

Since then or when I created this thread. I installed a Cam, AFR Heads, Stealth Ram, Headers, 30lb injectors, 3000 stall, Corvette tranny Servo/shift kit, and 3:73 gears. The car runs fantastic at WOT, but is rich at part throttle and while luggin in OD on a slight incline will kind of missfire below 3000 rpms. I purchased a Kirbin AFPR to replace the stock Stealth Ram FPR, but suspect it just needs something other than a mail order tune to fix the part throttle off idle air fuel ratio.

For reference I had no issues with the South Bay AFPR that I installed with the TPI unit before I did all of the mods. It worked as advertised with no issues. I just couldn't use it any longer with the Stealth Ram.

southbay08

not sure what the problem is. Just contact us and let us take care of it for you. We sell these regulators constantly. If you have a problem....once again call us
516-442-4707

george88gta

it was NOT your regulator! I removed it and had some metal shaving from a junk 9 injection rail plug that was replaced with a quality one. It holds pressure now!!!!!