Why do LB7 injectors fail?

Bersaglieri

Bersaglieri

Ron Swanson's Brother
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Jan 8, 2008
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LB7 injectors fail, but I've never seen anyone explain how or why. I'm curious, anyone wanna tackle this one?

If it's already been covered here please post a link. I read some theories on Dmax forums, but some of those sounded more like guesses.
 
What I have heard and read is the lack of fuel filtration is the main cause of injector failure. But I am def not a duramax wiz though.
 
Entrained air, poor filtration, water, and poor design all contribute. Bosch specs a 3micron filter, most ACDelco and aftermarket replacements are 7mic.

I've also been told that their location under the valvecover exposes them to much more heat, contributing to early failure. I haven't seen anything that makes me want to believe it, but I can see where it might make a difference.

An aftermarket lift pump will help eliminate air and provide much better filtration and better water separation. I've been told that a lift pump will make a massive difference in injector life. Personally, I think if you intend to keep it near stock, a CAT filter (1um) and frequent changes ought to be good enough.
 
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Heat is what I've been told and the only reasonable explanation. There are "revised" injectors but they fail also, plenty of guys have eaten through a set with AirDog filters with the stock filter in place. Maybe where the injectors are oriented in the head have something to do with it, perhaps they are too close to an exhaust passage, idk.
 
Just my opinion...but after all these years of owning LB7s, I've fallen on the side of excessive heat. LB7 injectors fail whether you add extra filtration or not. They fail whether you use additives or not. They fail whether you add a lift pump or not.
So whats different between LB7s and later models? Hot oil temps under the valve covers + high firing voltage. It makes sense.
GM moved the LLY injectors outside, but kept the voltage up, and the problem dropped in frequency. They lowered the voltage on the LBZ, and the rate fell more. Failures do still happen in both models, but nowhere near as frequently as the LB7.
 
As everyone else said, poor filtration. The initial bosch injectors for the LB7 were taken directly from Europe. Their fuel is much cleaner than ours, providing less wear and more lubrication. Basically due to the differences in fuel the design did not hold up in the US.

Any LB7 injectors bought now should last.
 
Great info guys, much appreciated. I'm actually looking at an LB7 truck, hence the thoughts about the injectors. My buddy who's a GM dealership guy said the LB7 owners that are meticulous about filter changes, maintenance, and don't do stupid heavy hauling get 100k or more out of injectors just fine. However he's seen them go real quick on people who neglect their trucks.
 
On my 5th set now and 6th set is going in this month... We haul very heavy and hear may be the culprit, 400k miles and 6 sets is still ****ty
 
pre 2008 ( I think, maybe 07) LB7 injectors had non chrome ball and seats which also caused the leaking injectors/high return rates that is/was very common with them.
 
Six sets?!?! Damn it's got me rethinking the nice LB7's I've found lately.
 
i work at a gm dealership and have installed multiple set of injectors on LB7's. alot of them i find where the edge filters on the injectors are clogged with dirt. id have to say its a lack of filteration and dirty fuel.
 
I'm sure Weston could provide a very good answer for the op's question.
 
TheBac said:
Just my opinion...but after all these years of owning LB7s, I've fallen on the side of excessive heat. LB7 injectors fail whether you add extra filtration or not. They fail whether you use additives or not. They fail whether you add a lift pump or not.
So whats different between LB7s and later models? Hot oil temps under the valve covers + high firing voltage. It makes sense.
GM moved the LLY injectors outside, but kept the voltage up, and the problem dropped in frequency. They lowered the voltage on the LBZ, and the rate fell more. Failures do still happen in both models, but nowhere near as frequently as the LB7.
Click to expand...

For the record the voltage information does not tell the story. The LB7 injectors on the early release had metal and heat treat problems. The newer replacement injectors changed that to the same metal and heat treatment as the LLY and LBZ injectors. The coils on the injectors for the LB7's take much higher current flow so that could be an issue but most of all the injector failures with LB7's are not coil failures. For the most part it seems to be excessive return fuel which is cause by dirt in the seat area or a worn seat. Maybe the addition heat under the valve cover helps cause that issue but I do not know. The LLY and newer have a slightly different seat arrangement in them so that too could be the answer but who knows.
 
I'd gladly take any info I could get from Weston, he's pretty particular about details. Regardless it looks like we've collected a lot of info here. If I come across anything else I'll add it later.

As of Saturday I officially own another LB7. Since the "new" injectors have 30k on them already I'd like to do as much preventative maintenance on them as possible. I'd like to address any filtration issues I might have by keeping on a filter changes. Someone local was telling me I needed to run a different fuel filter than factory replacements because they don't filter small enough microns. I was going to pick up a WIX fuel filter today when I went for an oil filter. Should I be looking else where for a special factory location filter or should I be looking above and beyond into FASS or something else?
 
20 days after getting my LB7 I had #5 stick wide open. I replaced just #5 and a week later #4 was wide open. My local diesel techs are puzzled at how/why they are going from not problems to wide open without warning at city speeds. I'm currently doing the other 7 and hoping for the best, but because of this, I am thinking about unloading the truck altogether. Damn shame cause it's a spotless truck from Texas...
 
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