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Thread: LS3 Engine running Rich

  1. #1
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    LS3 Engine running Rich

    Test drive File Jasmin, 83 jimmy ls3 PSI change o2 min.max drive 2.hpl

    Hi there All,
    New here and just getting started with HP Tuners.
    I have just finished a new GM crate LS3 in a 83 Jimmy. Using PSI wiring harness ECM and TCM. 4L75E.
    It is running rich all the time with long term fuel trims @-19 to -25 consistently. O2 sensors are switching normal but low.
    To start I was getting a Random Missfire code p0300 and ran -25 LTFT. I adjusted the O2 min/max rich lean to 450mv for both.
    now running -19 LTFT and getting rich codes on both banks. I am thinking there is a way to adjust for altitude. or just adjust flow rate?
    we are at 3900 ft.
    can anyone point me in the direction to adjust fuel. Just want to make sure I am using the right Adjustment.
    Current Tune File Jasmin, 83 jimmy ls3 PSI change o2 min.max.hpt
    Thanks in advance

    20211124_122536[2926].jpg

    Tyler
    Last edited by tyler@theshopturnervalley; 2 Days Ago at 02:31 PM.

  2. #2
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    What's the fuel pressure? Describe the fuel system and plumbing. That's where to look first, not the tune file.

  3. #3
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    thanks for the quick response, After the post I did check the fuel pressure, 70 psi. seems hi. All new lines with
    New Tanks Inc. fuel system including tank to fit the 83 jimmy with in tank pump, corvette fuel filter/regulator with return.
    I believe the ECM controls the pulls width for the pump. but also thought the fuel filter has a built in regulator.

    Tyler

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    Do you have an exhaust hooked up, or just running headers?

  5. #5
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    That fuel pressure is too high. I dislike the corvette filter/regulator combo. If the pump is too powerful it just overpowers that filter.

    On a vehicle swap like this I doubt you are using the factory fuel pump control module, so the computer isn't controlling anything pump related.
    2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.

    If you don't post your tune and logs when you have questions you aren't helping yourself.

  6. #6
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    the job is finished minus tuning, running headers with 3" dual and cross over pipe.
    Corvette filter/regulator Tanks ink 4 series pump. that does put out 70 psi.
    wondering if I can tune for that or should I add a regulator?

  7. #7
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    Quote Originally Posted by 5FDP View Post
    That fuel pressure is too high. I dislike the corvette filter/regulator combo. If the pump is too powerful it just overpowers that filter.

    On a vehicle swap like this I doubt you are using the factory fuel pump control module, so the computer isn't controlling anything pump related.
    ... I agree, the pump is overpowering the regulator in the filter, wondering if I can tune for it or best to add a in line regulator?
    was hoping the PSI/Tanks inc system was plug n play as everything was purchased new and as a system.

  8. #8
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    I had a similar problem with my pump overpowering the vette regulator/filter. Was showing varrying fuel pressure from 70 psi at idle to 62 psi under load. I ended up tunning around it by chaging my min/max fuel pressure and adjusting the flow rate table by calculating injector flow rate per fuel psi. I used a stock 08 vette tune with my swap that had a 58 psi flow rate across the board, which is what the vette regulator should be governing to. My situation is more complicated then yours, as i swapped an l92 escalade motor into a stick shift car. Used the vette tune as a base and had to retune ve and maf, as they were way off due to the different cam profiles. Your swap sounds like a simple plug and play with the ls3 crate. Easiest fix would probably be to just install a regulator on the rail and ditch the other one, if fuel pressure is indeed the problem.

  9. #9
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    Quote Originally Posted by Leva View Post
    I had a similar problem with my pump overpowering the vette regulator/filter. Was showing varrying fuel pressure from 70 psi at idle to 62 psi under load. I ended up tunning around it by chaging my min/max fuel pressure and adjusting the flow rate table by calculating injector flow rate per fuel psi. I used a stock 08 vette tune with my swap that had a 58 psi flow rate across the board, which is what the vette regulator should be governing to. My situation is more complicated then yours, as i swapped an l92 escalade motor into a stick shift car. Used the vette tune as a base and had to retune ve and maf, as they were way off due to the different cam profiles. Your swap sounds like a simple plug and play with the ls3 crate. Easiest fix would probably be to just install a regulator on the rail and ditch the other one, if fuel pressure is indeed the problem.
    thats what I'm leaning toward, totally agree. I'll know for the next one. unfortunate to redo the fuel system as it looks great, but performance first!!!

  10. #10
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    A return style regulator makes it way more complicated, lots of stuff in the tune has to be changed. For a setup like this all you need is a fixed, stable, correct 58psi supply. Easiest fix is a pump that isn't mismatched with what the rest of the combo needs - second easiest is a NON-REFERENCED regulator mounted in the rear that simply dumps anything over 58psi back into the tank.

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    Have a regulator on its way to replace the Vette filter with inline filter and regulator, will send update shortly.

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    Thanks for the info from everyone.
    I to be honest missed the obvious by not checking the basics.
    fuel pressure was as said by blindsquirrel and yes was the issue. I had installed a Tanks Inc. system that delivered 70 psi.
    I assumed what was ordered was a kit for what I was installing. nothing in the install instructions mentioned a regulator.
    tunes seems to be working well.

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    Quote Originally Posted by 5FDP View Post
    That fuel pressure is too high. I dislike the corvette filter/regulator combo. If the pump is too powerful it just overpowers that filter.

    On a vehicle swap like this I doubt you are using the factory fuel pump control module, so the computer isn't controlling anything pump related.
    As well you got it. I don't know why I didnt check pressure first. probably too excited to play with the tuning!
    live n learn.

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    How did you install the regulator? Out back with a return to the tank like blindsquirrel suggested? Im thinking of ditching the vette regulator as well. Car runs decent, but slightly rich during transients and tip in. Believe its due to that 70 psi im getting at idle. I can probably keep tinkering with the tune to correct, but having a constant fuel pressure would make life much easier.

  15. #15
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    Quote Originally Posted by Leva View Post
    How did you install the regulator? Out back with a return to the tank like blindsquirrel suggested? Im thinking of ditching the vette regulator as well. Car runs decent, but slightly rich during transients and tip in. Believe its due to that 70 psi im getting at idle. I can probably keep tinkering with the tune to correct, but having a constant fuel pressure would make life much easier.
    regulator.jpg

  16. #16
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    removed old filter and used inline. for simplicity mounted the regulator on the frame rail. once pressure is set no need to have it in a handy spot.

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