Boost leak/injector questions

[Delta.Speed]

After much looking and driving 6 hours, I was able to land a 3500 dually. 2004 LB7 4x4. 240k miles. Neat two-tone interior, bose audio, heated seats, power mirrors, dual zone ac, fog lights. Seems it was a pretty loaded truck back in its day.

Overall solid truck, got it for cheap cause the guy thinks it has injector issues.

I dont doubt it since it's an LB7, and the guy has had it since 30k miles and says he has never done the injectors.

However, while test driving it, I noticed something odd. I think the truck has got to have a MASSIVE boost leak. I could hear it clear as day on acceleration. It sounds like an air nozzle hooked up to a shop compressor.

The truck smokes black on acceleration. And the scanner says at WOT it's getting 16-17ish lbs of boost. Once it's underway, the smoke diminishes, and it's barely even visible. Sometimes, it is not visible at all. But you get on it and again, and again air rushing sound and black smoke.

The injector balance rates are all over the place on this truck. But 4 of them are especially bad at +/- 3.9X ish, and one of them is at 4.35.

So here are my questions.

Can a major boost leak mess with the injector balance rates to the point they look like there's bad injectors when there aren't?

Does 16-17 pounds of boost at WOT sound right? Or is there definitely a boost leak there? If the psi is right, what else could make that air leak sound?

Does it sound like I've got one issue here with multiple symptoms? Or is it multiple separate issues and the truck will need injectors no matter what?

Here's a picture of the truck on my flatbed.

Thanks in advance for your invaluable know-how.

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[TheBac]

Check the metal IC piping on drivers side, down in front of the tire. Theres a very common rub point right there. Check all boots and clamps on IC piping, too...might have a weak boot.

 

[wydopenLb7]

Bad injector usually presents itself as grayish haze at idle when the truck is warm.

The MAP sensor can only read to 22psi of boost so I wouldn’t rely on what the scanner is reading. Pressurize the system with an air compressor and find the leaks. Can spray the boots with soapy water if they aren’t obvious.

Once you fix that drive the truck and see if there are any bad injector symptoms.

 

[Delta.Speed]

Well it definitely has a haze at idle when warm. Hard to see in the photos but its definitely there.

So with the injector balance rates, the mileage, and with the haze. No way around it, injectors are definitely bad?

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[DAVe3283]

Highly likely the injectors are toast. You can diagnose them further if you want. Balance rates are part of the equation, but you want to look at the main fuel rate on hot idle with the A/C off and in park. Should be 7-10 mm³, generally as the injectors fail they leak so that drops. Seen some as low as 3, but anything under 7 is really suspicious IMO.

The other thing to keep an eye on is the oil level. Some early injectors (which it sounds like these might be original) would crack and leak diesel into the crankcase.

Finally, if you stand behind the exhaust, if it has a strong diesel smell that burns your nose or stings your eyes, then the injectors are bad. This is assuming it doesn't have a major mechanical issue like low compression, but 99% of the time on a LB7 it is injectors.

You should post more photos of the truck. I know GM did 2-tone interiors on the Suburban, but I have never seen one on a truck before. I wonder if someone took Suburban parts, or combined 2 truck interiors, or maybe it was a rare factory option? Either way, curious to see it!

 

[Delta.Speed]

Highly likely the injectors are toast. You can diagnose them further if you want. Balance rates are part of the equation, but you want to look at the main fuel rate on hot idle with the A/C off and in park. Should be 7-10 mm³, generally as the injectors fail they leak so that drops. Seen some as low as 3, but anything under 7 is really suspicious IMO.

The other thing to keep an eye on is the oil level. Some early injectors (which it sounds like these might be original) would crack and leak diesel into the crankcase.

Finally, if you stand behind the exhaust, if it has a strong diesel smell that burns your nose or stings your eyes, then the injectors are bad. This is assuming it doesn't have a major mechanical issue like low compression, but 99% of the time on a LB7 it is injectors.

You should post more photos of the truck. I know GM did 2-tone interiors on the Suburban, but I have never seen one on a truck before. I wonder if someone took Suburban parts, or combined 2 truck interiors, or maybe it was a rare factory option? Either way, curious to see it!

Well I can say with certainty that standing anywhere near the tailpipe of this truck is like letting death slowly take a hold over you lol

I tried to put the tag on it while it was running and I wasnt able to get through the first screw without walking away and shutting it off cause the haze coming out the back of it was unbearable to be around. Eyes teared up, throat and nose got itchy. I had to step away... my other LB7 is nothing like that. So if that means dead injectors, then these are toast cause it is terrible to be back there while the thing is running.

I'll check the oil level in a bit again, but when I checked it at the seller's place, it seemed normal.

Will definitely post more pictures of the truck. To my ignorant eyes it looks like it may have been a fully optioned truck when new.

It definitely has alot more buttons than my 02.

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[DAVe3283]

Yeah, those injectors are long gone from what you describe.

The good news is they now make the updated SAC-style injectors for the LB7, which seems to take care of the short injector life. You can get them in stock size if you don't want to run a tune ("SAC00") or a lot of people go with the 45% oversize "SAC45" version as it is cheaper, but it does require a tune. You can of course go much larger if you have plans to make a ton of power down the road, but even the SAC45 should be good for 500+ WHP.

 

[Delta.Speed]

Here she is. Rough around the edges, but it was the cheapest, running, driving, rust free truck I could find. Working AC, 4x4 and 6 brand new Firestone tires were the cherry on top for me.

Worst case scenario, I'm confident I can get my $5k back parting it out. But I dont see why I wouldn't be able to get her back in good shape.

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[Delta.Speed]

Yeah, those injectors are long gone from what you describe.

The good news is they now make the updated SAC-style injectors for the LB7, which seems to take care of the short injector life. You can get them in stock size if you don't want to run a tune ("SAC00") or a lot of people go with the 45% oversize "SAC45" version as it is cheaper, but it does require a tune. You can of course go much larger if you have plans to make a ton of power down the road, but even the SAC45 should be good for 500+ WHP.

Yeah Brad set me up with some SAC 45s for my 02 LB7. And I just had him quote me some SACs for this truck.

I used to be afraid of the bad reputation the job had, but once I got into it I found its not as bad as people make it out to be.

I feel alot more confident doing them now after I had to do the job 3 times cause of faulty SCD billet hold downs. So now I'm targeting mostly LB7 trucks for my business.

I have another 04 LB7 3500 to go buy this weekend that looks to be in mint condition, but the injectors are also out on that one. The guy said he'd take $7k for that truck. I think its worth it for a 190k mile mint condition truck with only injectors to do.

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[TheBac]

Previous owner did the two tone paint and interior. HDs only came single color ext and int from factory.

 

[Delta.Speed]

Previous owner did the two tone paint and interior. HDs only came single color ext and int from factory.

Damn then the original owner was a baller cause the dude I bought it from was the second owner. He got it with 30k miles and he showed me pictures of it from when he got it in 2006 and all this was already done by the original owner.

So the original owner bought an 04 truck brand new, interior swapped it, did a custom paint job on it, and then sold it at 30k miles....damn.

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[TheBac]

Yep. Only the 1500s came with the lower silver or beige color paint as an option.
As for the seats, Im almost 100% sure those are aftermarket covers. They dont match the two-tone factory stuff.
Its easy to change interior plastics and door panels to make the two tone interior, though.