2007 Silverado E38 4.8 Gen4 Wont Idle After Return Fuel System

Hello,

i recently installed a return fuel system with an A1000 pump and 1250cc injectors.
i currently can not get truck to idle. it was running and idling fine before with no issues.
we ran out of injectors and needed to put larger ones in.

attached are the two tune files.
return fuel system tune, i increase the stoich table by 2.18 and divided the injector flow rate and afr term by 2.18
the delta table i set at 63.5

i increased the idle to 950 instead of 800, but that didnt seem to help.
it falls past it and cant recover and dies.

any help is greatly appreciated!!

also im no longer reading fuel pressure in the vcm scanner. i have the pressure sensor connected inline on the frame rail where it was on the stock system.
edit:after further thinking, it would make sense that im not reading and fuel pressure into the ECM because its located in the return line.
will have to move it to the supply line.
does the ECM require the fuel pressure signal to run correctly?

Quote:

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blindsquirrel
Can't do it by 2.5, the Stoich table will only accept a max of 32. 2.5 would put that one over the limit at 36.7. Max you can do is... (fiddles calculator)... 32 divided by 14.68... 2.18 or something? That will only require a little fudging to the point the tuning process will take care of it.

Multiply Stoich (ECM 12300) by 2.18. Divide Injector Flow Rate (ECM 12307) by 2.18. Divide IVT Terms: AFR Term (ECM 12560) by 2.18.

If this is still returnless it's not going to be happy with the flow rate. In vacuum IFR will be substantially over 63lb. If it's got a real boost referenced regulator it'll be fine, the flow rate will always be 63 (x 2.18) because the pressure delta never changes.

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my original thread: https://forum.hptuners.com/showthrea...ark-Axis-Scale

Injector Offset table is still set up as if it was a returnless system.

What is your new base fuel pressure? Whatever that PSI corresponds to in kPa, copy that column and paste it across the entire table. Because your pressure delta is always the same whether there is vacuum or boost in the manifold.

returning fuel make no difference at all to the data, its only if u have manifold referenced the fuel pressure with a mechanical regulator ? also scaling the stoich if it dosnt fit fuel wise then needs some airflow scaling which affects all tables that use the g/s value, if ur at 58psi or 43.5psi rail pressure also changes all injector data if ur manifold ref

Quote:

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Originally Posted by blindsquirrel

Injector Offset table is still set up as if it was a returnless system.

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is this what you are referring to?
the injector offset selection? change form vacuum to MAP?

Attachment 115185

Quote:

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Originally Posted by blindsquirrel

What is your new base fuel pressure? Whatever that PSI corresponds to in kPa, copy that column and paste it across the entire table. Because your pressure delta is always the same whether there is vacuum or boost in the manifold.

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my base fuel pressure is the same as before 58 psi.
correct i put 63.5 across the injector flow rate vs pressure delta table.

Attachment 115186


thank you very much for your help!!

Injector offset vs. volts has an axis that references pressure. The table would need a single value set across the pressure range. Similar idea as your Flow rate vs. Pressure delta table.

Attachment 115187

Hi. Thank you for the help!!

i changed those settings and still cant get it to idle
my lambda is like 0.75 when trying to idle.
ive tried increasing the idle from 900 to 1150, just to try to get it to idle but it just falls down to 500 and then dies.
the only way i can get it to stay running is to hold my foot on the pedal and keep it above 1000 rpm with like 15% throttle body position.
which seems pretty high just to keep the truck running. is there a way to check the commanded throttle position?
i see the electronic throttle in the airflow section, but the table doesnt appear to be linear or just based on throttle position and then percentage opening.
its based on RPM or VSS for some reason.

my thought is that not enough air is getting into the motor to mix with the fuel being provided.

no matter what i do, the lambda value will not come up.
i have lowered the fuel pressure to 30 PSI and it stays at 0.75 lambda.
i have cut up to 90% of the fuel out of the VVE table and it stays at 0.75 lambda.

the only way i can get it to come up is buy holding the throttle or disabling injectors in the the VCM Scanner.
when i disable two injectors, it will come up to about 0.93 lambda.
the truck will not run though unless i hold the pedal down some.

attached is the tune in the truck currently and some screenshots of the injector data.
20211123 is whats currently installed.
20211124 is what i was looking to install. i have injector offset-vac and map options to try. not sure which to go with. but default was vac.

in the injector data it says the min pulse with is 0.0725, however HP will only let me set 0.0727
in the short pulse adder table, the axis rows do not match my injector data excel sheet but the number of cells is correct.
the other issue with this table i have is that i can not set the values from the excel sheet into the table. when i enter the values, hp corrects them to the numbers shown in the screenshot.
im sure these are complicating my issues but i dont know how badly.

any help is greatly appreciated.

i would also like to try to convert this to the 2 Bar OS to get rid of teh VVE table that just keeps changing my numbers.
are there any thoughts on if that might help fix my issue?


thank you very much for your time and help!!


Attachment 115394
Attachment 115395
Attachment 115396

try this as u didnt fail the maf right, also i put stoich back to double to keep it in scale if ur rich u have to take it out with fueling which if maf wasnt failed properly ur prob still using its values which may explain why ur adjustments to vve didnt do anything see how this goes