2016 L83 w/LT4 pump erratic fuel pressure

[silvy423]

Myself and my buddy (tuner) have been dealing with and torubleshooting an erratic low side fuel pressure issue. I attached both and idle log and the current tune to see if anyone has some input on this matter. Let me lay out some details about the truck as it may all be tune related, I just don't know at this point.

2016 Silverado with L83 6L80E combo
76mm Turbo setup
32% Cam lobe camshaft
DOD delete
LT4 HPFP
LT4 fuel injectors
-6 PTFE Hose with AN fitting directly into the HPFP
E85 sensor
DSX Aux fuel system
LT2 Intake
LT5 Throttle body
3200 Stall

What I have done to troubleshoot thus far.
Installed new low pressure sensor-no change
Totally disabled the DSX and capped the T fitting- no change
Installed OEM in tank pump-no change
Installed OEM Fuel pump control module-no change
Installed OEM LT4 feed line/check valve prior to HPFP-no change

The initial thought was the LT4 high pressure pump was not set up correctly in the tune-
The lack of factory check valve prior to HPFP could have allowed pulsing back into the feed line
The large fuel lobe cam could be giving a jack hammer effect on the fuel line giving erratic pressure
I went ahead and installed the factory check valve hose (GM 12642289) and no change

Not sure what could be causing this??? My buddy who is helping me tune says its a real issue and we need solid low side pressure to tune properly. I have another tuner telling me its not a huge deal as long as we are not having high side issues, the desired VS provided high side seems fine. we have not seen any indication that the combo of intank L83 pump and DSX aux pump cant keep up with the highside desired pressure. a_3-2-2022_ric_maestas_16_lt14_turbo (1).hptTurbo Silverado IDLE w ck valve.hpl

[Dominatorstang]

I am pretty new to GenV and never owned a 5.3l so I have read your post a couple times but probably can not offer much help.

I do notice the LT4 HPFP is a common swap and the fuel lobe you have is pretty common so I would think once the right person sees your tune then they can say if it looks okay.

What changes have you done on the tune from stock to reflect the LT4 HPFP, injectors, and larger fuel lobe?

[Dominatorstang]

I can say my fuel pressure on low side and high side were not following commanded well at all when I first installed my cam on my L86. It had me worried something was wrong, but once airflow and virtual torque started to dial in then pressures started to line out.

[silvy423]

I truly hope this is a virtual torque setup issue. As it seems like most issues are with Gen V

[TriPinTaZ]

I made some changes to the low and high side config. If you have a separate FPCM you will need to license and flash these changes to the FPCM. If your setup is like the Corvettes and Camaros then you would just need to flash the ECU. See if this helps.

fuelpumpchanges.hpt

[Jonblarc7]

Did you measure for the lash cap on the fuel lobe? TSP gave me the wrong size for my 32% over and insisted it was the right size. It wasn't and after failing two HPFP i measured for the right one.

[silvy423]

Did you see some things that needed changed? I will flash tomorrow and see if it improves.

[silvy423]

I bought the tool for measurements. It?s the LT4 pump with 32 fuel lobe and LS7 lash cap

My high side fuel pressure stays good vs demanded and actual. It?s just the low side that?s erratic

[Jonblarc7]

I have a L86 stock HPFP with a TSP 32% over. They said to use the comp cams lash cap. But it measured to big, It was a few years ago so I don't remember by how much. So I have the LS7 cap now.

[Chrisisiced]

Did anyone ever figure out a fix for this kind of issue? I'm seeing the exact same thing happen in my 2016 camaro SS with LT4 HPFP and LT4 LPFP.

[Racerbox77]

bump

[Racerbox77]

I bought the tool for measurements. It?s the LT4 pump with 32 fuel lobe and LS7 lash cap

My high side fuel pressure stays good vs demanded and actual. It?s just the low side that?s erratic

What did you find was the issue?

[lynmup]

These threads get started and never offer a solution...Use the search function they say...geez!

[TriPinTaZ]

It's likely the HPFP was measured incorrectly and was destroyed. The low side inconsistent readings were likely the tuning or they just noticed the "bug" where the low side fuel pressure gets reported sporadically and with zeros in VCMScanner making it look like there is something wrong with the low side.

[smokeshow]

These threads get started and never offer a solution...Use the search function they say...geez!

The solution is our port injection controller coming out later this year

[TriPinTaZ]

The solution is our port injection controller coming out later this year

would ya hurry up already?

Where do I pre-order lol

[smokeshow]

would ya hurry up already?

Where do I pre-order lol

We're not doing pre-orders but I'll accept money into my pocket for nothing. Like a tip in advance basically. Lol

[lynmup]

The solution is our port injection controller coming out later this year

Is there no reason the stock pump couldn't be updated to handle all the fueling needs? I see Snow Performance has a tripple in tank fuel pump that is said to support 1300+ on E85. Too bad this came out after I already bought the Armageddon 475 for nearly the same price. Summit Racing sells a 535 LPH I could just swap out for my 465 if the need occurs. The port injection controllers in my opinion just add too much under the hood and too much complication. I did look into competetors pricing and I could by another used car for what they were wanting.

[TriPinTaZ]

Is there no reason the stock pump couldn't be updated to handle all the fueling needs? I see Snow Performance has a tripple in tank fuel pump that is said to support 1300+ on E85. Too bad this came out after I already bought the Armageddon 475 for nearly the same price. Summit Racing sells a 535 LPH I could just swap out for my 465 if the need occurs. The port injection controllers in my opinion just add too much under the hood and too much complication. I did look into competetors pricing and I could by another used car for what they were wanting.

You can throw all of that Low Side fuel at the car sure, but what are you going to do about the high side? There is no high side pump that is out right now that can support 1300+ HP on E85. Port Injection kits are not complicated and DSX is about to make it even easier. I think you might not have the latest info available based on your comment.

[lynmup]

You can throw all of that Low Side fuel at the car sure, but what are you going to do about the high side? There is no high side pump that is out right now that can support 1300+ HP on E85. Port Injection kits are not complicated and DSX is about to make it even easier. I think you might not have the latest info available based on your comment.

Currenlty, the LT4 HPFP is footing the bill with the increased 32% lobe. The FIC 30%+ injectors are staying fed at 2400 psi. Just attempting to solve the common P2635 code (which I disabled) and the modulating fuel pressure which I hope to remedy with the LPE check valve that wil be arriving this week. Unfortyunaley, one of the fittings will be next week.

I think 1,000 WHP in the Yukon in my signature is well enough. Drives like a stock SUV and gets up very well. Suprises a lot of people, even myself sometimes as I forget how much it has under the hood as it feels so tame at times. It's just money afterall!