LS swap won't fire.

[audiophile]

I am brand new to this site and have a steep learning curve ahead. I have watched hours of youtube videos and read for hours on this and other forums. I have a 72 C10 that I swapped a 2005 Sierra 4.8l into, with a turbo setup. My problem is I cannot get it to start. It will crank, sputter for 3-4 seconds and die. AFR does seem high, but I thought I did everything right. We thought the ecu was VATS deleted before, but it wasn't so the plugs are pretty soaked (maybe the problem?). Can someone help me by looking at my build and tune to see if I am missing anything? I thought I did a datalog, but I cant find it. AFR was rich, around 9 or 10, that's all I can remember.

2005 4.8l DBW
Same ecu as the truck
3 bar map from efi source
IAT from 95 Jimmy

I did;
delete vats
maf to 0
delete p0101-p0103
delete egr code
scaled decapped factory injectors to 75#

[blindsquirrel]

You have P0103 set to No Error Reported, meaning that if the MAF is not installed, it cannot run the test for P0103, and if it can't run the test it can't set the DTC as 'Current' and without that DTC set it cannot run in speed density.

You're using a non-boost-referenced, returnless fuel system?

Decapped injectors seem like the greatest thing ever, like finding $100 bills just laying on the ground, but by chopping the ends off you essentially create a brand-new injector with totally different Offset & Short Pulse Adder specs, which will forever remain a mystery unless you send them off to a lab and have them professionally re-characterized, which costs more than just buying real, quality aftermarket 80lb injectors that come with all the correct data in the first place. Flow rate is literally the least important of all the injector data.

[5FDP]

You don't delete the MAF codes, the most important code for speed density is P0103. It needs to be MIL on first error.

Decapped injectors are pretty sketchy and often suck for tuning. Likely will have to pull fuel from the VE depending on what fuel pressure you are trying to run.

[audiophile]

Well crap, I thought I set it to fail on first and then delete SES. Thank you so much guys for catching that. I am not married to the decaps, its just what I had. I have heard they are a pain, if they are flow matched are they still a pain to tune with?

[blindsquirrel]

Flow testing won't tell you anything about the other, more important, characteristics that got changed by decapping.

[audiophile]

Thank you blindsquirrel. I didn't realize it altered more than just the flow. I thought the bad rap for de-caps was because people just de-capped their 8 injectors and didn't bother cleaning or flow matching them and it caused tuning problems. i.e for example a dirty injector(s) may flow 20% less than the other injectors and you just cant tune the difference, causing tuning problems...

To answer your previous question
"You're using a non-boost-referenced, returnless fuel system?"

Yes, it is a returnless system. as far as non-boosted reference, yes I just wanted to get it started, and idle...

[blindsquirrel]

They will work fine at WOT, since the pulsewidths are always going to be relatively large there. Where they will frustrate you to no end and run you around in circles is at small pulsewidths, where having the correct Offset/Short Pulse Adder data is super important.

0.3125ms (or whatever, just a random number in the plausible range) added to 20ms is essentially nothing, but that same 0.3125ms added to 1.5ms is pretty huge.

[Alvin]

Decapped injectors are pretty terrible.

I just had a 5.3 NA stock cam hotrod swap dropped off with them and I had to pull them because they just wouldn't clean up down low.

[audiophile]

They will work fine at WOT, since the pulsewidths are always going to be relatively large there. Where they will frustrate you to no end and run you around in circles is at small pulsewidths, where having the correct Offset/Short Pulse Adder data is super important.

0.3125ms (or whatever, just a random number in the plausible range) added to 20ms is essentially nothing, but that same 0.3125ms added to 1.5ms is pretty huge.

Squirrel, You have a great way of explaining things, I truly appreciate it!!! Not only did you answer my question, but you happily explained it and in depth.

So below is the turbo I have, what injector recommendations do you all have? Size and brand? I am a huge boosted Subaru guy (14' WRX, no I do not vape lol, I am an old man as well) so I run ID's in it, but I am completely open to what works well for a turbo LS.

Working Pressure: 25 PSI
Compressor: 72mm Big Compressor Wheel
Turbine: 0.81 A/R
Compressor Wheel: 72.1/102.4 MM
Turbine Wheel: 74.1/64.6 MM

I am looking at running somewhere between 7-14#, stock block. I just want a really fun street truck, so I can set my wastegate etc at whatever level works best. I am not planning to run it on the strip or do launches, so I am not too worried about my trans etc.

[blindsquirrel]

So like... 750hp @ the crank? If so, that only needs 54lb-hr. But that's assuming 58psi base fuel pressure and a 1:1 referenced regulator. If it stays non-referenced/returnless, any boost above atmospheric has the same effect as reducing fuel pressure by the same amount (your 58psi base spraying into a manifold that's at 14psi makes the injector flow drop the same as if you had 44psi fuel pressure). So injectors will need to be sized bigger to compensate (62lb-hr to get 750 crank with 44psi and non-referenced).

That said, real injectors cost real money, you should probably ask the (reputable) injector companies what you need. FI(Clinic) has an easy calculator you can play with here if the numbers above are off. https://fuelinjectorclinic.com/flow-calculator

[audiophile]

So like... 750hp @ the crank? If so, that only needs 54lb-hr. But that's assuming 58psi base fuel pressure and a 1:1 referenced regulator. If it stays non-referenced/returnless, any boost above atmospheric has the same effect as reducing fuel pressure by the same amount (your 58psi base spraying into a manifold that's at 14psi makes the injector flow drop the same as if you had 44psi fuel pressure). So injectors will need to be sized bigger to compensate (62lb-hr to get 750 crank with 44psi and non-referenced).

That said, real injectors cost real money, you should probably ask the (reputable) injector companies what you need. FI(Clinic) has an easy calculator you can play with here if the numbers above are off. https://fuelinjectorclinic.com/flow-calculator

I would even be happy with 400-500 hp. Dang squirrel that is mind blowing, I never realized that! Do you tune for people, professionally?

Yeah I have played with their site. I was just planning for 14 psi and calling it a day, wherever my HP lands that's what it is, if my "system" cant do 14# then I am fine going down to 7#. I am just going for a "budget" fun street truck. I.e. fun>hp#

[blindsquirrel]

Thing is, a 60lb injector costs the same money as an 80lb injector from the same company. Doesn't make any sense to go any smaller than what the combo is capable of, there's really no downside. Modern big injectors are mostly fine at low PWs. Hell, GM put 51lb injectors in 350hp flex fuel 6.0 L96s and they run fine on straight gasoline.

I AM NOT A TUNER! Retired dealership guy who always played with hotrods on the side, I only tune on my own dumpsterfire stuff.

[blindsquirrel]

And I have to mention that those L96 injectors can be had for super cheap. Those $55 injectors, with a 1:1 fuel system, would be able to support more power than any street-compound tire could realistically handle. Like 690hp at the crank/600hp wheel.

edit: As long as we're talking gasoline, no E85.

[audiophile]

Yeah I completely understand that. My WRX has 1050's so I can run flex. I am still breaking it in and am only at 18#, but my DC is crazy low, like 32%.

That is super cool! Your knowledge and willingness to help us Newbies is commendable! At times I think my life is a dumpsterfire lol, but sometimes you have to enjoy the huge flames lol


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[blindsquirrel]

Any updates on getting it to run? It should at least do that even with the decap injectors. Maybe not well, but it should run.

[audiophile]

It is at my "mechanics" house and I can't go there until tomorrow, but I am chomping at the bit to try it out. Once you and 5FDP said P103 I realized I fat fingered it and that's probably it. I also just got my 2 bar map so I will put that in to make tuning etc (RTT) easier. I really want to get it running so I can get it to temp to check fans, leaks, throttle pedal working, dash gauges etc.

[audiophile]

Any updates on getting it to run? It should at least do that even with the decap injectors. Maybe not well, but it should run.

Woohoo! She started and actually ran really good. Idled smooth, revved up smooth. AFR was around 16, so a little lean, but I am extremely happy! It has been a long time coming! Thank you all for your help! I truly appreciate it!