Need Help With Start-Up Tune

[SZMX14]

I need help with my tune as im at my wits end with it. I have experience with tuning Gen 3 LS engines for cam swaps. This current one is fighting me heavily. The usual tricks to make them start are not working.

Setup is in a 2003 Silverado 1500, 5.3 LM7, 78/75 turbo, TSP Chopacabra Cam (.550" I/E valve lift, 108LSA, 214/222, 106ICL), 706 heads with springs, 9.5:1 CR. It is set up on a 3 bar OS with a GM 3 bar Map Sensor, currently running stock 25lb injectors until i get the start-up dialed in. Ive tried it with MAF and without, properly failed and properly reenabled either way. Have an adjustable FPR as well but have tried both with stock FPR and my new one. Ive managed to actually get the truck to start and run with the adjustable FPR and with MAF but i was lucky to even get it to light off in the first place. Currently, only the exhaust side of the turbo is hooked up. Intake for the turbo is not hooked up until i can get a solid start-up while NA. All sensors are hooked up, IAT is accurate, MAP reading is calibrated to 100kpa key on, engine off. Truck will spit, sputter, pop, nearly hit, but wont fully fire off. The ONLY way i can get it to possibly even fire up is if it hasnt been attempted to start in a while. Has to be stone cold to even have a chance to fire off. Ive tuned a setup with this cam before with zero issue and was very easy to get running. This one has been a headscratcher thats been fighting me so if i can get any tips of what to check in my attached tune file, it would be greatly appreciated! Attached is also a log of a start-up attempt. Setup is also DBW. Thank you.

03CateyeBaseTuneChopacabraTurbo4L80EMAFDisabledClosedLoop3BarSpeedDensityBoostEnrichAdjusted25lb.hpt
StartAttemptFailCateye.hpl

[blindsquirrel]

That's great, but what is the actual measured fuel pressure at the rail? Does it run if you spray it with brake/carb cleaner? Does it run if you go full pedal and put it in clear flood mode (shuts off the injectors)?

Is 305/15 the correct linear/offset for your particular MAP sensor? Use of the phrase 'calibrated to 100kpa key on' is a little... well.

[blindsquirrel]

There's no P0102/P0103 set as 'Current' in that log, but that can not show up if the logfile is taken during the first IGN cycle after a reflash. Does it get the MAF codes if you scan it live? Can you please add the MAF Sensor Status PID so it will show 'MAF Fail' in real time whenever you're logging?

[SZMX14]

That's great, but what is the actual measured fuel pressure at the rail? Does it run if you spray it with brake/carb cleaner? Does it run if you go full pedal and put it in clear flood mode (shuts off the injectors)?

Is 305/15 the correct linear/offset for your particular MAP sensor? Use of the phrase 'calibrated to 100kpa key on' is a little... well.

58psi

Nope, doesn't help
Flood clear doesn't help either. The "best" sputtering or attempt at starting is at about 50% throttle.

Map linear is at 305, offet had to be set at 60 in order to show 100kpa key on, engine off. At 10.33 it showed 50-51kpa, at 15 it showed 55-56kpa

[SZMX14]

No MAF codes come up when scanned
I can add it, yes

[blindsquirrel]

Map linear is at 305, offet had to be set at 60 in order to show 100kpa key on, engine off. At 10.33 it showed 50-51kpa, at 15 it showed 55-56kpa

So... the tune file is not the one used for the log you posted? Cause Offset in that file is 15, and the log shows 99.something at KOEO..

If you have to guess at the Offset, how do you know the Linear is correct? What is the sensor? Does whoever sells it not know its specs?

[blindsquirrel]

Is this still using the rear mount cam sensor, or is converted to front mount with one of those extension harnesses that are ALWAYS pinned wrong?

[SiriusC1024]

58psi

Nope, doesn't help
Flood clear doesn't help either. The "best" sputtering or attempt at starting is at about 50% throttle.

Map linear is at 305, offet had to be set at 60 in order to show 100kpa key on, engine off. At 10.33 it showed 50-51kpa, at 15 it showed 55-56kpa

GM MAP Data and PN.png

[edcmat-l1]

58psi

Nope, doesn't help
Flood clear doesn't help either. The "best" sputtering or attempt at starting is at about 50% throttle.

Map linear is at 305, offet had to be set at 60 in order to show 100kpa key on, engine off. At 10.33 it showed 50-51kpa, at 15 it showed 55-56kpa

What is the part number of the "GM 3 bar map sensor"?

If it won't run on spray, and the plugs aren't fuel fouled, you have other issues. Need to test for spark.

[SZMX14]

So... the tune file is not the one used for the log you posted? Cause Offset in that file is 15, and the log shows 99.something at KOEO..

If you have to guess at the Offset, how do you know the Linear is correct? What is the sensor? Does whoever sells it not know its specs?

The tune file I posted might not have had my offset and linear saved when I posted it to the thread. I was playing around with linear and offset trying a few things but there has been no change. When i can actually get it to start, it runs great. I have a genuine GM 3 bar map sensor from a 2012-2015 supercharged camaro.

[SZMX14]

Is this still using the rear mount cam sensor, or is converted to front mount with one of those extension harnesses that are ALWAYS pinned wrong?

Nope, still a rear mount cam sensor, gen 3 harness that originally came with the truck. Truck was running and driving perfectly fine before torn down when it was still stock

[SZMX14]

What is the part number of the "GM 3 bar map sensor"?

If it won't run on spray, and the plugs aren't fuel fouled, you have other issues. Need to test for spark.

55567257

Blue labeled LSA/LS9 MAP sensor

Plugs do get fuel fouled at times and can smell fuel from the exhaust when it doesn't start.

[gtstorey]

Linear 312.5
Offset -11.26
https://dsxtuning.com/products/gm-3-bar-map-55567257

[SZMX14]

Linear 312.5
Offset -11.26
https://dsxtuning.com/products/gm-3-bar-map-55567257

Will try that to see if it changes anything

[blindsquirrel]

It should run on brake/carb cleaner unless it's got too much fuel. Disable fuel pump or injectors, make sure plugs are clean, then try it on spray. It should run well enough on an occasional toot of spray that you could drive it around a little.

[blindsquirrel]

Stock 25lb injectors... from a different app than what the tune file is from? Tune is for a 2005 L59 which had 36lb injectors. Have you verified via the numbers on the injectors that they are what you think they are?

36lb injectors with the PCM calculating the pulsewidth using the 25lb in the file will deliver ~40% more fuel than intended.

[SZMX14]

It should run on brake/carb cleaner unless it's got too much fuel. Disable fuel pump or injectors, make sure plugs are clean, then try it on spray. It should run well enough on an occasional toot of spray that you could drive it around a little.

Right but that wouldn't exactly help to why it won't start with its own fuel

[SZMX14]

Stock 25lb injectors... from a different app than what the tune file is from? Tune is for a 2005 L59 which had 36lb injectors. Have you verified via the numbers on the injectors that they are what you think they are?

36lb injectors with the PCM calculating the pulsewidth using the 25lb in the file will deliver ~40% more fuel than intended.

Actually the 25lb were stock on the 05 that computer came from, stock fuel injector data is 25.2lbs and the injectors I have are legitimate stock 25lb

[blindsquirrel]

The VIN in your file: 1GCEC19Z85Z180299. Z = L59. L59 = flex fuel. Injector numbers 12580426/88894361/89017586.

screenshot.21-03-2024 12.15.45.png

[SZMX14]

The VIN in your file: 1GCEC19Z85Z180299. Z = L59. L59 = flex fuel. Injector numbers 12580426/88894361/89017586.

screenshot.21-03-2024 12.15.45.png

The computer was perfectly fine with 25lb injectors before the cam and turbo. This was a daily driver before the swap and had no issues with runnability and is ran with the same injectors