“Cab off” means the shop removes the truck’s cab to get to parts underneath that are difficult to reach. It usually indicates a big, labor-intensive repair, not a quick fix.
DEF is a special liquid diesel trucks inject into the exhaust to help clean up pollution. When a truck first starts using DEF (like these 2011-era trucks), you can see new types of problems compared to older diesels.
Term
DPFEGR
DPFEGR is an emissions-monitoring system related to how the truck recirculates exhaust gases. It uses sensors to make sure the EGR system is doing what it should, and the speaker is saying that wasn’t the big problem compared to other issues.
“No start” means the truck tries to start (cranks) but the engine won’t actually run. With fuel-pump problems, the truck often can’t build enough fuel pressure.
If metal debris gets into the fuel, it can wreck the truck’s fuel system—especially the high-pressure pump that has to pressurize fuel precisely. That can lead to the truck not starting or losing power.
Term
granating
“Granating” sounds like the contamination turning into gritty particles. Those tiny bits can act like sandpaper in the fuel system and help explain why pumps fail.
They’re saying the truck’s fuel pump broke. If the pump can’t deliver fuel correctly, the engine can start running poorly and other fuel-system parts can get damaged. That’s why they also replace injectors and clean the fuel tank.
Injectors are the parts that spray fuel into the engine in the right amount. If the fuel system gets contaminated—like after a pump failure—injectors can get damaged too. That’s why the shop replaces them as part of the fix.
They remove the fuel tank to clean out any dirty fuel or debris. If the pump failure sent junk through the system, that junk can still be sitting in the tank. Cleaning it helps prevent the new parts from getting damaged again.
They’re asking whether multiple trucks failing means there’s a bigger underlying cause. Sometimes it’s just random, but other times it’s something shared—like a common part or setup—that affects many vehicles. That’s what they mean by a systemic problem.
A “dealer” here refers to the authorized sales/service network that can observe failure patterns across customers and report them back to manufacturers. In reliability discussions, dealer-level repetition can be an early clue that a defect is widespread. The transcript uses a “one dealer” example to argue the issue is happening broadly.
CP4 is the name of a high-pressure fuel pump on certain diesel trucks. Some owners worry about it failing because if it breaks, the truck can run poorly or need costly repairs to the fuel system.
The fuel filter is like a screen for your diesel. It helps keep dirt and other junk from getting to the pump and injectors, so changing it on time matters.
“Top tier fuel” means a gasoline/diesel brand that meets stricter cleanliness standards. The goal is to keep the fuel system cleaner and reduce the risk of problems caused by dirty fuel.
“Stock emissions compliant” means the truck is set up the way the manufacturer intended to meet emissions rules. If you add aftermarket parts, the dealer may require you to return it to factory setup for emissions-related work.
A lift pump is a small fuel pump that helps move diesel from the tank to the engine. It makes sure the high-pressure pump gets fuel more easily, which can help prevent expensive failures.
Fuel contaminants are things like dirt or water that get mixed into the diesel. They can wear out or damage the expensive parts that handle high fuel pressure.
A water separator removes water from the diesel fuel. Since water can cause problems in the fuel system, catching it before the pump helps prevent damage.
Air Dog is a brand of aftermarket fuel pump kit for diesel trucks. People use it to help deliver cleaner fuel and protect the expensive high-pressure parts.
CP3 is another type of high-pressure fuel pump used on some diesel trucks. The speaker is saying CP4 is the one people worry about most, but CP3 can fail too.
They’re describing it like insurance: pay a smaller amount regularly to prevent a big expensive breakdown later. The idea is to reduce the risk of a major fuel-system failure.
“LML” refers to a specific diesel engine used in some Chevy/GMC trucks. Here they’re talking about problems and fixes that are common to that engine’s fuel system. The upgrade ideas are meant to help the truck keep running reliably.
Term
twin kit
A “twin kit” in this context refers to an aftermarket dual-lift-pump setup (or dual-pump arrangement) intended to improve fuel delivery and reliability on the LML. The hosts mention Jamie had to get rid of his for the twin kit, implying the twin-pump approach was part of the upgrade path. They’re also discussing failures (blown fuse/no-start) that can happen even with upgrades.
“Gelled up” means the diesel fuel gets thick in cold weather. When that happens, fuel can’t flow properly to the engine, so the truck may be hard to start or stall. It’s one of the classic winter diesel problems.
Manually priming means you help push fuel through the fuel system so the engine can start. If the lift pump fuse fails, the truck may not get fuel normally. Priming manually is a way to temporarily get it running again.
A sump is like a small “fuel collection” area at the bottom of the tank. It helps the pump keep getting liquid fuel instead of sucking air, especially when the tank is low.
The sending unit is the factory part in the tank that helps with fuel pickup (and fuel level reading). When you add a lift pump and push more fuel, the stock pickup can become a bottleneck.
A corrugated hose has grooves inside that can make it harder for fuel to flow. The speaker is saying the factory version is restrictive, so the pump has to work harder.
“Quarter tank issues” means the truck starts acting up when the fuel gauge is around a quarter full. The idea is that the factory pickup can’t reliably feed fuel at that level, especially after modifications.
A fuel system saver is an add-on meant to protect your diesel fuel system. The goal is to reduce the chance that a failure sends damaging debris to the expensive parts.
Term
CP for fails
“CP” sounds like a fuel-system part that can fail. The speaker is saying the upgrade is meant to stop that failure from damaging the injectors.
A fuel pressure regulator is a valve/control that keeps fuel pressure at the right level. That helps the engine get the correct amount of fuel consistently.
This means cleaning the fuel tank and dealing with the fuel pump area. If there’s dirty fuel or metal in the tank, cleaning it helps prevent the problem from coming back.
Diesel engines use a fuel system that squeezes fuel to very high pressure before it’s injected. If something in that system starts failing, the truck may not start or may run poorly because the engine isn’t getting the right fuel pressure.
Car
2015 LML Duramax twin turbo
This is a specific GM diesel engine (the LML) used in a 2015 Duramax truck. It’s turbocharged, and the discussion here is about common reliability problems the shop sees on that engine.
If the fuel pump is failing, it can’t pressurize the diesel correctly. That can cause the truck to not start or to start poorly because the engine isn’t getting the right fuel pressure.
“CP three” is the shop’s shorthand for a particular version of an aftermarket setup/calibration they installed. They’re comparing it to other versions based on how reliably trucks behave afterward.
Term
CP four
“CP four” is another version of the shop’s aftermarket setup. The tech is saying they see more problems with that version coming into the shop than you’d expect from forum talk.
LBZ is a code name for a particular Duramax diesel engine generation. The speaker is using it to compare how often certain problems show up on different Duramax years/engines.
The AC compressor is the part that makes your truck’s air conditioning work. In this job, it can get in the way, so the tech may have to move it to reach what they’re installing.
Diagnostics means figuring out what’s actually causing the problem, using checks and tests. On diesel trucks, it’s especially important because fuel-system problems can be caused by contamination or pressure issues. The segment is about learning the real cause after a bad repair.
A relief valve is a valve that helps control fuel pressure so the system doesn’t over-pressurize. If you find metal on it, that usually means something inside the fuel system is wearing out and sending debris through the lines.
The “snowball effect” here describes how initial contamination in a high-pressure diesel fuel system accelerates failure. Once metal particles circulate, they can damage regulators and other precision components, which then increases the amount of debris and worsens the failure chain.
A “CP3 conversion” means more than just swapping the pump—it’s the work needed so the rest of the fuel system matches the new pump. Shops decide what else is required based on the truck and how you want it to behave.
They’re talking about choosing parts based on what you care about most: making more power or making the truck more dependable. In this case, the CP3 is treated as the reliability-focused option.
LB7 is a specific generation of GM Duramax diesel engine. The point here is that on those trucks, if a pump failed you could often replace just the pump instead of reworking the whole fuel system.
Common rail is how many modern diesels deliver fuel. The engine keeps diesel under high pressure in a shared line, then sends it to the injectors when needed. The CP4 and CP3 are parts of that high-pressure system.
In this context, “500 horsepower” is being used as a practical power target to decide how aggressive the fuel-system reliability upgrades need to be. The host implies that moderate output can be supported with CP4 protection (system saver + lift pump), while higher targets require a more robust pump strategy. It’s not a universal threshold—just the rule-of-thumb being discussed.
Term
67 800 horsepower
This is the speaker’s example of a much higher power goal. Their point is that when you’re chasing big horsepower, the CP4 setup won’t be the best choice for reliability. They’re saying you’d move toward a CP3 at that level.
Fleece is a company that makes aftermarket parts for diesel trucks. The speaker is listing it as another kit option people install for better reliability.
CP4 is a type of high-pressure fuel pump on some diesel engines. When it “fails,” it can start making metal debris or stop working correctly, which can then damage other fuel system parts.
A class action lawsuit is when lots of people with the same problem team up legally instead of suing one-by-one. Here, it’s mentioned because many truck owners were affected by the same kind of fuel-pump issue.
Bosch is a company that supplies parts to car makers. In this discussion, they’re mentioned because their CP4-related components are part of the fuel-pump problem story.
A “recall” is a manufacturer-mandated fix for a safety or emissions-related defect. In this segment, the hosts describe how recalls can include swapping the high-pressure pump (CP4 to CP3) at no cost to the owner.
Warranty work is paid by the manufacturer, while customer-pay work is paid by the owner. The shop’s labor reimbursement can be different, which can change how repairs are handled.
“Weak links” means the parts that are most likely to cause problems first. The host is saying that on this diesel setup, the fuel system is usually where you should focus. Fixing those trouble spots is the best way to improve long-term reliability.
The “low side” is the part of the fuel system that feeds fuel forward at lower pressure. If it can’t supply enough clean fuel, the engine’s high-pressure fuel components don’t get what they need. That’s why the speaker treats it as a reliability weak point.
The “high side” is the part that makes diesel pressure high enough for the engine to inject it correctly. If it’s not building the right pressure, the engine can run rough or not make power. The speaker is saying fixing these high-side problems is part of making the engine last.
Inside some turbos are small moving parts that control how much boost you get. If those parts get stuck, the turbo can’t work correctly and the truck may feel off or even require a turbo replacement.
A burnout is when you spin the tires while the engine is working hard. The idea here is that extra heat and load after the truck sits can help loosen parts that have gotten stuck.
A head gasket is a critical seal inside the engine that keeps hot combustion and coolant separated. If it fails, the engine can start mixing fluids or losing coolant, which can cause overheating and major damage if ignored. The host is saying this is a known weak point on these Duramax engines.
Deck clearance is a measurement related to how the engine’s top surfaces line up when the head is installed. It matters because if the surfaces don’t match up correctly, the gasket may not seal. The host is describing a check he does before putting everything back together.
Head bolts are the big bolts that hold the cylinder head tightly onto the engine. When you take the head off to replace a gasket, those bolts can be stretched or weakened, so shops commonly replace them to make sure the seal stays tight.
A timing belt is a belt that keeps the engine’s timing lined up—so the valves open when they should. It’s a scheduled maintenance item on many engines. If it breaks, it can cause major engine damage.
Glow plugs are diesel engine heaters that help the truck start and run when it’s cold. If they’re old or failing, the truck can start poorly, and the heat they create is important for proper combustion.
The head gasket is a critical seal inside the engine. If it fails, the engine can overheat or lose compression, and the repair is usually expensive—so the point here is that small issues can sometimes turn into big ones.
“Pulling the heads” means taking the top part of the engine off. It’s usually necessary for big repairs like fixing a head gasket. Because it’s a lot of work, it can be expensive and takes time.
A “diesel tax” means diesel fuel costs more because of extra taxes or fees. That can make it harder to “save money” with a diesel truck, even if it uses less fuel.
“Fuel mileage” means how far the vehicle can go on a gallon of fuel. Higher fuel mileage usually means you spend less on fuel over time.
LIVE
Welcome to another episode of the Diesel Performance podcast with your host Chris Emke and Anthony
Bernini.
Dude, how you doing?
I'm vibing, dude.
How are you?
The vibes are pretty good.
You know, it's a Tuesday.
Yeah, it's a Tuesday.
Almost off on my day, right?
And you know, the weather here in Illinois starting to pick up, a little humid, some
rain here and there, but I would say the temperatures and everything else are kind
of on an incline.
Fuel mileage is going up.
Fuel mileage is going up.
You know, so that's just, you know, I don't know if it's a new tune or what, but mileage
is going up.
Can you put a new tune in?
Nope.
But maybe the tune learned.
Yeah.
You know, I hear that a lot.
The tunes will get better or go bad with time.
Yeah, for sure.
So as long as you get a good one, then I think you'll be, they get better over time.
Another thing that we get called in a lot about at the shop is just overall general questions
on, I would say like the L and L Duramax.
Yeah.
And I think a lot of that is, is you have, you have guys that have either A owned these
trucks for a bit now wanting to start to play with them, or you're starting to get the guys
who can afford them secondhand, you know, they're starting to age a little bit there
and they want to know like, Hey, what to do, what not proper maintenance this
that.
So we decided that we wanted to get Nick over in the, in the shop, a mechanic Nick, super
tech Nick, not old owner, you know, consultant Nick, you know, we wanted to get mechanic
Nick here.
So we have Nick Everton of calibrated power.
How are you?
Done good.
How's everything going?
Fantastic.
How's the shop life?
A little hot down there.
Yeah, it's a little humid, right?
It's shop life.
Yeah.
So for our listeners who, who don't know you, I know you haven't, there's some, there's
some mug, mug, mug shots of you, if you will, on our website doing some installs and things
like that.
But, you know, you've been in the diesel world for a little bit.
Why don't you give us just a brief little background on you and the diesel space?
All right.
Well, I mean, I was at the dealer for about 12 years.
Okay.
And floated around a little couple of independence and I'm here about a year now.
And you've, I mean, we've known each other for a very, very long time.
A hot minute.
Like we used to, for any of the listeners, we lived kitty corner from each other as
children.
Really?
Yeah.
I didn't even know that.
Yeah.
We lived one street away from one another.
Like dude was so young around diapers, like that young and we were never probably the
fondest of one another as kids.
And then rekindled again during high school, we had shop class together.
And then, you know, now here we are years later working together.
So it's pretty, pretty wild.
But yeah, yeah.
No, for sure.
Now in those times, you've also done some, you know, between the dealer background stuff
like that, you've also done some projects, right?
You had an LB7, LBZ stuff like that.
You helped me with my first diesel, actually.
And that was like a full like cab off.
Oh yeah.
Cab in the yard.
Yeah.
Cab in the yard.
Oh, no, there's more to the story.
Tell the rest of the story.
I used a Jeep and a winch cable, lifted the cab off the frame.
With a tree?
Yep.
It's on your Facebook.
It's there.
It's documented.
Did you live in Machesney Park at the time or what?
Jesus.
But the truck ran and drove.
Oh, it ran.
Good numbers.
550, 500, I don't know.
It was a solid running truck, sold it, and the guy was loving it as far as I know.
Trucks still running.
Yeah.
One of the things that I've always respected about you specifically, I don't trust a lot
of people in the mechanic space, you know, we have our shop manager, DJ, been friends
with for years.
I trust DJ with my life when it comes to him working on my stuff.
But you're right there.
Like you're at that top tier, top caliber.
I know that you could work on something, you're very in depth.
You document what you need to document, you're very knowledgeable.
I know that you work on something, the truck ships.
It's good to go.
Yeah, I appreciate that.
I take a lot of pride in my work.
No, it goes a long way, right?
Yes, it does.
Now, with that being said, coming from a dealer background, you were at a dealer when LMLs
were around.
I think, you know, probably the dealer life, that was the platform, Frank.
It was totally the platform at that point.
I remember when they came out in 2011 and got to see all the new issues that they had
and 11-12 was horrible, 13-14 was getting better, and we kind of rolled off of them.
What were some of the issues?
Just out of, because I was in high school.
You're a newbie coming into this now.
Yeah, I was very young at the time.
A lot of missions, I mean, but mainly that reductant tank.
Yeah, I mean, it seems like that's been something that GM has been plagued with for throughout
the years with that.
But you think about it, 2011 is the first year of DEF for that platform, and I don't
really remember too many DPFEGR problems.
I feel like it was more DEF, reductant tank, more related.
A lot of heater issues.
What outside of that, from being at the dealer service warranty stuff, outside of that, did
you see a lot of, at this point, CP4s weren't a thing?
They weren't broadcasted a thing, but I have had 12,000 miles on a truck, 5,000 miles on
a truck comes in, tow in, crank, no start, and what do we find?
We didn't know that metal was a thing, and my first CP4 that failed, it didn't catastrophically
fail.
It just produced no pressure.
And when I took it out, it all looked normal on the outside, but GM wanted, nope, we need
that.
Okay.
So put a new pump in it, shift it down the road.
So when you were starting to see these fuel systems with the metal contamination, was
GM originally kind of chalking it up?
The dealer chalking it up is, oh, it's fuel contaminants.
It's not the pump itself, it's just contamination.
Because we get these in all the time, we get questions on them.
It's neat to ask these questions, because again, not something I thought of, like, yeah,
from a dealer's side in the tech, when these trucks are first starting to roll out, like,
what was GM's kind of response to something like that?
So back then, we didn't see as much granating as we do now, kind of.
And if we did see it, yeah, we put a whole new fuel system in it, cleaned out the tank
made sure everything was clean, dry, and pretty and happy.
Putting all the exact same parts right back in?
Same parts back in.
There was no fix-ish, if you may.
But we're also talking 2012, 2013.
Yeah, that was in the beginning, and it was not a hush-hush, like you're saying, Tony,
of, oh, don't tell anybody.
We just, hey, your pump failed.
It came apart.
We're replacing your injectors, dropping your fuel tank, cleaning that out.
We got to put fresh fuel in it, and then we get the customer back on the road.
Truck would be happy.
We used to have the knowledge that we do now back then, gotcha.
Sanon was trying to keep secrets.
He was just like, hey, here's the fix.
This is what we think is the issue, and then gotcha.
It's just like no different than what we do here at the shop, right?
You have one issue, it's like, okay, I'm going to note it.
Second issue, okay, note it.
Third or fourth, like is this a coincidence, or is there something more systemic or a bigger
problem here?
I could see that, and that was just one dealer, right?
Yeah, yeah.
That's happening all over.
Martin, Shavie, and Crystal Lake there.
We got quite a few diesels in, and I'd say, I don't even know how many systems we put
in, because it wasn't like every truck was failing.
It was hit or miss on the amount that we had coming in, and the changeup of the emissions
lights as well.
It wasn't a fuel system, it just, yeah, it was a fair mix.
That'd be very accurate.
I mean, you see that even to this day, right?
Yeah.
We'll fast forward to now for that guy that calls in saying, man, I was on the forum, and
CP4s, I'm just deathly afraid to drive this truck anywhere.
I got to change it.
I got 10 other customers with 200,000 miles on their wigs, no issues.
Totally.
It's not every truck is going to have a problem, and I think we've learned a lot over the
years with them, and I think that's really where you're going to run into some of these
upgrades that we're going to talk about today, but I feel like a big, big thing of it is
just fuel contaminants or lack of maintenance, not changing your fuel filter or being the
lucky one to get a bad batch of fuel somewhere or something along those lines.
That is a very solid point, and that's what we always advise our customers.
Top tier fuel, that will keep your CP4 from failing, and like Chris said, we will go into
performance upgrades that will help that CP4, but back at the dealer, you're all stock emissions
compliant.
We can't change or upgrade it.
We have to put the factory stuff back out.
Yeah, you're not going to put aftermarket stuff on there.
I mean, that kind of segues into our, I should say, a few modifications we've got that you
kind of noted down is a mechanic, like what you like to see on trucks or what you like
to do.
The first one on the list is a lift pump.
We're talking about fuel contaminants, issues with CP4s.
We've got lift pumps on there from, I mean, we're all pretty familiar with them.
From your point of view, why should guys be putting lift pumps on their truck?
We already kind of covered it, but do you want to go a little bit more in-depth on why
you like to see them on there?
So, the rural thumb that I've always said to my customers and clients, a fast system
will take a contaminant from eight micron down to two micron, so that way the contaminants
are not in your pump.
And it's also supplying your CP4 with pressure rather than the CP4 doing the work and sucking
the fuel from the tank.
So yeah, pump doesn't have to work as hard in any sort of contaminants that might end
up making their way up to the pump, ideally get caught in the filters and just reduce
the risk of something bad happening to the rest of the fuel system.
I've always liked to utilizing and keeping the factory fuel filter and route as it's
that pathway going into the CP4.
So now you have the water separator, you have the fuel filter on the fasts or air dog, whatever
lift pump of your choice, then you run that through the factory lift pump as well.
And I guess for me, it's just like, I know what the cost is of a CP4 failure or any
high pressure fuel pump failure at that point, like, I'm not saying CP3s are the most, you
know, like, no, no, but it could happen.
So an extra point of filtration and an extra 60 or $70 fuel filter every 10,000 miles,
like to me is kind of a drop in the bucket from from that insurance perspective.
That's I always kept it on mind because I mean, unless you're doing like a twin turbo
kit or something like that, which, you know, you got to get rid of it there.
Yeah, but I mean, because we'll get horror stories.
I mean, you know a little bit more than I do, like Jamie's LML, he's had to get rid
of his for the twin kit.
And I mean, it seems like a couple of winners in a row.
He'd blow a fuse and like his truck wouldn't start as the lift pump was granted.
It was gelled up and whatnot, but not say that having a factory fuel filter head would
have solved that, but I know that that can kind of play in there as well.
There's also we're going to back into Jamie's truck again here, because
there's a couple of things as we talk about other upgrades that we've seen work specifically
on that truck.
So, yeah, you know, one last little touch on that.
Keeping the stock housing on there.
You have a primer.
Yeah.
So you if that lift pump ship, if the lift pump fuse pops, you can prime it manually
and get the truck started again and drive it with a failed lift pump fuse.
Yeah, that's a smart move to hit that.
I might I'll be seven.
The lift pump took shit in the winter and like I brought it in, let it fall out and
primed it from the filter head and I was able to drive until exactly Saturday to Monday
until I get a fuse put in there for looking for the listeners.
A lift pump on the LMLs.
I know once you get into 11, 14, 15, 16, like they kind of group them different.
How much work labor time are guys looking at to put a lift pump on one of these trucks?
It's definitely half a Saturday to put one in.
OK, you've never done one before.
Yeah.
You can add a sump as well with your lift pump with, which is most people do.
What's the what's the reason behind that?
To get the fuel from the bottom of the fuel tank.
So as you're improving performance,
the stock sending unit will restrict as that pump needs a better diameter hose.
OK, the factory, the corrugated hose itself is more restricted than depending on the years.
That's why you get a lot of LML guys that will complain that their pumps are loud.
Yeah, because it's like drawing a fast or air dog.
Like if you talked to any of those guys, those pumps are made for pushing, not pulling.
So if you have it more restrictive, working harder, it's gravitating.
That's another addition.
Another big thing that I see a lot of or that we run into is in the early days
of tying into the factory, sending unit, you know, as we would with with Duramax.
The trucks tend to run into the quarter tank issues a little bit more predominantly.
So I like the sumptuous for the fact that it's been a year since I've heard
the quarter tank is I'm ever been dealing with some for how long?
I mean, never since you started. Yeah.
So I mean, making that recommendation.
It's been a long time since I heard that.
I forgot about that.
So you have you have a 2011 LML, right?
Trucks new to you, bone stock.
You're like, hey, I'm doing this lift pump, right?
You're going to spend the half a day in your in your driveway doing it.
What other things are we looking at?
What's kind of that next kind of upgrade that you would recommend to somebody?
So if we're keeping her on the cheaper side, cost effective,
the fuel system saver, OK, I think is a.
Good way to protect your pocketbook.
If the CP for fails, it will keep the injectors whole, hopefully.
Yeah. So that way it doesn't send extra metal through
because of how I see before fails.
It continues to send metal with the fuel as it's delivering it to the injector.
That was one of the cool products that I, you know, extra G came to the table
with years ago, you know, having that upgraded.
Essentially, it's just an upgraded fuel pressure regulator
with a reinforced net and a tighter micron, I believe.
We've had the luxury of seeing that part actually work.
Yes. So I have, you know, I had a hot shot or had a power stroke forward.
And the guy put 100 and 40000 miles on the truck
in two years and we had done a fuel system at like 200
And CP for failure did a whole high pressure system.
And the truck came back to us like two years to the date almost.
Yeah. With like 300 and 45000 miles on this truck.
And the truck came in as a crank, no start.
And, you know, we pulled the regulator and do just metal, right?
That that second go around was a pump and a tank cleaning.
It was a whole high pressure system.
And then you mentioned earlier, Jamie, right? Yeah.
General manager here over at Calibrated.
He's got a really cool, you know, 2015 LML Duramax twin turbo
cool build that was an emissions on build that we did years back.
And when we originally did that truck, it had a CP for 10 mil, right?
With a system saver and 70,000 miles in, dude.
Truck, no crank, start once again and pull the regulator.
Regulator was all, you know, metal all over it.
The pump was failing.
And at that point, we ended up, you know, swapping to a CP three
and doing a CP three, 10 mil on that.
But, you know, there's there's two hands on trucks that I've seen come in
and out of the shop that the system saver did its job.
Now, we work on a ton of trucks over at the shop.
I can kind of one hand, how many times I've seen CP four failures come into the shop.
We'll get customers that call in with that.
But, you know, trucks coming in with total failures like that,
I feel are a little bit more scarce or limited
than than what the general public, the forums say.
I feel like it's also kind of at least in my experience,
where they talk about LOIs with blown head gaskets.
It's like, OK, well, I'll get calls on them.
But like, I've had LBZs with more.
Oh, how does that LL?
Yes, LL is more, I think, more than anything.
And there's been similar ones where it's like, oh, LBZs crack pistons.
Like, well, I've maybe seen one or two of them here,
but I've had like three or four LB7s that have had it.
You know, granted, it depends on who you talk to, blah, blah, blah.
But no, no, my car count is LL crack pistons.
Yeah, if we're going to go deep and if you're going to go into it for sure.
Now, on those fuel system savers,
what kind of labor, what does like an install look like?
Is that another few hours in the garage?
That is a few hours in the garage.
If you can move the AC compressor out of your way
and you have the right tool set up.
Yeah, you can sneak the old regulator out,
put the new regulator in and start the truck back up.
I still think it's nuts how something that,
I mean, physically that small and that cost effective
can save you thousands and of dollars.
Because, you know, to Chris's point, the guy comes in for a full fuel system.
We do all the bells and whistles, clean it out, injectors, lines,
go through everything.
And then if he didn't have that fuel system saver,
who knows how much money he would have spent again.
Well, I'm going to go for an average fuel system, 12 to 14 grand.
Yeah, I mean, you know, maybe do it on the light side.
I mean, we just, we did an LLM fuel system recently
and it was, you know, a $10,000 job with shop labor.
And that was with no lift pump or failure
because failure adds to dropping that tank,
yeah, all the metal in the tank and in the lines.
Oh, yeah.
And then the I've also been on the tail end of, you know,
helping walk through diagnostics with a customer
who took a truck to a said shop.
And that shop did the, you know, the total fuel system
and they didn't clean everything out appropriately.
And they just contaminated the whole new system.
That's not a bad day.
Yeah, that's a very bad day.
I mean, we've seen, we've seen that.
We had an LLM in the shop recently that you worked on.
It was that 15 where a gentleman was having an issue.
He did a system saver.
He had an issue with the truck for a whole other year.
Then did a CP3 conversion, still had the issue.
And he was lucky enough.
I told this guy he needs to go to the casino, like he'll win.
But he ended up doing the system saver
when the system saver was starting to fail.
Okay, swapped it out and the pump lasted
on the whole another year.
Then he did a CP3, still running into this issue.
And there was contamination on the...
The relief valve.
On the relief valve, yeah.
So we pull it out and there's metal debris in there.
Like had that guy driven that truck
with the original regulator on the original CP4
just a little longer, that would have been
a catastrophic issue.
So he dodged a bullet.
Well, and that's how these pumps are failing.
Little, the contamination barrels really fast.
It's a snowball effect downhill at that point.
Is it just what's gonna build up on the regulator
and just a little bit more, more on the netting?
It's that metal that's, it's just circulating
through the entire system.
And that's gonna eventually eat away at the pump load, right?
And then the metal builds up on the regulator.
Well, then the regulator collapses
and everything gets pushed through
the whole high pressure system.
Geez, Louise.
So it's just, it's crazy to see how that,
like that domino effect takes place.
And then, I mean, I guess the next thing I kind of look at is
and there's two areas that you could look at, right?
And I think it really kind of depends on the pocket book.
But when would you incorporate
or when would you, when would you say,
hey, you know what, we're just doing a CP3.
Like we're just gonna CP3 swap this thing.
We're not doing a regulator.
We're not doing a lift pump.
Are we doing a lift pump?
Like when does that CP3 conversion come into the mix?
In my opinion, it goes off of clientele, right?
Like what is your next goal with your truck?
Do you want to produce more power
or have the reliability of a CP3 because old faithful,
I mean, you brought up LB7s,
that's what they had in them.
If they failed, you didn't replace a whole fuel system.
You replaced the pump.
And a pump, I don't know, 34 grand
if you're paying a shop to put a...
CP3 and everything, yeah.
So 34 grand's a whole lot better than 12
is the magic number in my head, yeah.
No, I mean, I kind of look at it as
it's six and one half a dozen in the other, right?
Like there's a lot of other diesel, common rail vehicles
that have CP4s and there's really not CP3 options
out there, right?
You just kind of run it.
I feel like the market has this stigma around the CP3
and don't get me wrong, CP3s are definitely more robust
and a little more resilient than the CP4,
but I think like to your point,
like what kind of power are you looking to make?
If you're gonna standard 500 horsepower,
then do a system saver and a lift pump, call it a day,
run the CP4, you know?
Yeah, you might need to replace it down the road,
but yeah, that pump's gonna fail
just like a CP3 is gonna fail with 300,000 miles, right?
Exactly, yeah, the pumps do fail, they wear out over time.
Yeah, and if you want to make more power,
you know, you want to get to that elusive
67 800 horsepower, well,
well, then CP4 really ain't gonna cut it for you,
you know, now you're looking at doing a CP3 at that point.
And on the topic of CP3s,
I know there's a couple different options out there.
Is there like a specific kit that you enjoyed installing
from a mechanic perspective, or do you got to go to?
Yeah, that, I mean, most of the kits
are very relative of each other.
I know before I came to this shop,
I had only installed Dan's diesels on mine.
It was just easy.
My supplier always gave me Dan's diesel stuff,
so when I came here, I got to install a Worley's kit,
an SNS kit, I've even seen this fleece,
they're all relative, very nice, they're all very nice kits.
And is that, I feel like again, from me,
that's got to be a lot more labor intensive
compared to like a lift pump or maybe like a regulator.
Very much, very much, you're tearing the toll,
full top half of the motor apart and getting it involved.
So that's not a Saturday afternoon garage.
I mean, I also feel like that's the guy who,
I'm gonna have this truck the next 10, 15 years,
I want to bulletproof this thing,
you're gonna get your money's worth
out of the pump and the labor versus the guy who,
listen man, I'm buying a truck,
I need this thing to last me two or three years,
I'm gonna off it, but this thing
is not gonna leave me stranded the next two or three years.
That's probably more of that system saver lift pump.
Yeah, exactly, I would agree with that, Chris.
Nick, how many CP4 failures would you say you've seen
from you being at the dealer to come into here?
But whether it be stuff you're doing for a buddy,
I mean, throughout the years, just throughout the total.
Throughout the years, let's just throw a number
on the years, 10 years, then the last 10 years,
I have seen probably only like 10.
Okay.
So one a year.
Yeah, not a big number, but still a decent number first.
How many LMLs have you seen in 10 years?
I don't have that number.
I don't have that number.
That's my point, you know, the cool thing is,
I think what's crazy is, is like, you know,
now you have like Chevy GM doing this
like whole class action lawsuit with Bosch on the CP4s,
and then you see Ram,
they took a completely different approach.
Yeah.
You know, 19 and 20, they had CP4s
and the dealer just recalled all the trucks,
like, hey, bring the truck back,
we'll swap it to a CP3, no cost to you.
I did not know they did that.
Under recall, that's how they do.
So it's crazy to see how the different manufacturers,
and then you look at Ford,
Ford to this day still has a CP4 in the truck.
I don't hear nearly as many CP4s.
Ford also has a supply pump, where the LML didn't.
Exactly, and that's our lift pump.
Would you think that Ram, part of the,
me just thinking, the reason they recalled those
is because it's a hell of a lot easier to replace a CP3?
I mean, it's literally an hour and a half job, yeah, yeah.
I mean, it's nothing.
I wonder like, if GM was gonna be like,
all right, we'll cover it, like what,
how much labor they would have to be able to do.
Well, I think like, too, like, isn't it like,
just calling the state of Illinois,
isn't like it law, you have to pay like one and a half times
what the, yeah.
So like, you have a mechanic working on it,
like you're, the dealer's paying.
Yeah, yes, the rate for warranty versus customer pay,
they put a line that they have to pay the tax,
the same rate the customer's paying.
Wow, pay up.
Run it up, dude.
See a bunch of LMLs in the parking lot tomorrow, shit.
So you kind of have that, right?
I feel like any LML customer that I,
that I talk to or any potential LML owner of sorts,
when they talk about reliability, dependability,
and longevity, it's always fuel system oriented, right?
Like that's the, that's the nip in the bud, if you will.
This is where you want to address,
these are the weak links to the LML.
Agreed.
If you, if you take care of the fuel,
the low side or the high side fuel system issues,
in my opinion, the LML in general,
is a pretty stout platform.
Like we've been playing with these things
for what, 15 years now?
Long time.
16 years.
Wow.
And I think like they've really shown
and proven themselves to be like a really, really,
really impressive platform.
Where do you go from there with upgrades?
Like you have the fuel system, it's reliable.
Are there other shortcomings of the truck
where it's like, hey, we should look at this or that,
or where would you go next to someone
who has one of these vehicles?
The turbo is a, I guess, next in line issue.
But as, but even back to an LBZ,
L-L-Y, they all have this similar issue
where the vanes will stick in the turbo.
It depends on some trucks or 30,000 miles.
I have an issue where they got to put a new turbo on it.
Yeah.
And the truck sits a lot, you find an LML with 30,000 miles,
man, that thing, cream puff.
I mean, I feel like every year that I take my truck
out of storage, vanes are a little sticky for a little bit,
until I do a couple of burnouts in that thing.
You don't do burnouts, but yeah, for sure.
What the shit, I'm trying to be cool on a podcast, dude, damn.
Well, I know our shop truck had an issue.
We had a 003A, granted that was a while ago.
We had issues with the vanes on that,
so I feel like it's either the trucks sit all the time
and that's when you have sticky vanes.
Or it's high mileage.
Super high mileage, and it's just like, yeah,
things are getting worn out, they're getting pissed off.
But otherwise, after that, that truck, that motor,
that platform, it's stout.
It's very stout, yeah.
I mean, we brought up head gaskets earlier,
of the LLY is always notorious for head gasket failures.
Well, the 2015, in my opinion, when I was at the dealer
for the LMLs, that was key.
I did so many head gaskets.
Really?
Yeah, yeah.
2015, really, really.
It was specific to that year.
Any idea why?
It would crack on the driver's side head gasket.
Same spot?
Same spot.
And then 16?
Second bolt from the back of the motor, top one.
Could pull off the head gaskets, look at them,
figure out my problem.
Obviously, we had to do both sides,
because you can't pressure check one side over the other.
So we were doing them, and I would check the deck clearance.
If it passed, it went back together with new head gaskets,
new head bolts, customer was on their way.
So let me ask you this, right?
Because you might get into some contradicting advice here.
Oh, boy.
If you were in the market for an LML,
are you looking for the lowest mileage truck around,
or are you looking for a middle of the road mileage
or a high mileage truck?
Like, where does your money get spent?
What's a value to you?
So back to that question, how long is myself looking
to keep the truck?
And I try to keep all my used cars,
because I'm a mechanic near that 100,000 mile mark.
Because that way, I know I can get another 100,000 miles,
at least out of it.
But people are usually getting rid of them at that mileage,
because they took it to a shop, and it needs
a bunch of stuff at that point.
Because I look at vehicles, they go to 100,000 miles,
and now you really have to do some maintenance to them.
Timing belts on some cars and whatnot.
But these trucks, it seems, brakes the front end,
all of that's about that 100,000 mile mark.
I think LML platform is when I first
seen a 200,000 mile brake job on a hot-shotter truck.
Really?
Yep.
He got 200,000 miles out of it.
Exhaust professional driver, should have done some work
on that one.
He did.
Clean his veins to the side of the Mississippi.
Right?
So yeah, now I would stay near that 100,000 mile mark
and do the general maintenance to it.
And at that 100,000 mile mark, blow plugs.
That seems to be, I mean, they're not spark plugs,
but they sure seem like it at that mileage.
It's scary to me when you talk to a guy who's
owned a diesel truck since new at Duramax specifically,
and you're talking about the general maintenance side of it.
And it's like, oh, when was the last time
your glow plugs were done?
Never.
What?
And we've had glow plug jobs turned into head gasket jobs
for that specific reason.
Oh, yeah.
Then breaking off.
And then people, guys will kind of like judge me,
where it's like, hey, man, maybe it's
good to routine doing glow plugs every couple of years.
And well, why?
They're not bad.
Well, it's because it's going to season the effin' head.
And then you got real problems.
Like the $400, $500 in glow plugs you're
going to spend, whether you're doing it yourself,
or then paying to have somebody do it
is a drop in the bucket.
Magical number, again, that $12,000 or more for a set
of head gaskets.
Yeah.
All just because?
It's because you wouldn't listen to your mechanic,
wouldn't listen to your sales guy.
I know I've had at least three or four head gasket jobs
where it was like, let's do glow plugs.
And then it's like, hey, we got two of these.
And I feel like it's always one in one head and one in the other.
And it's like, hey, man, we could try to get these out.
Yeah, go ahead, try to get out.
I got an extra car.
And it's like, hey, man, we need to pull the heads.
You didn't tell me this.
Yeah.
Brother, yes, I did.
No, I mean, I think I've probably discouraged guys
from dropping off their trucks to do head gaskets,
to do glow plugs, because I've always said, like, hey,
you've clearly already tried to do this and you've had issues.
Yeah.
If you drop it off and we can't do it and you want it fixed
right, this is what the end result is.
And it's not me foreshadowing, we're doing this.
It's just like, I want to be transparent.
I don't want there to be any surprises.
Oh, you told me there's only going to be X amount of money
to do this.
Well, in theory, in a perfect world, yes.
But clearly, you took it to one shop and you tried it
and you guys both couldn't do it.
And I'm not a miracle worker.
I mean, that's also the transparency that in the moment
no one wants to hear.
But then it's like, oh, maybe they
come back years down the road.
I was like, oh, that guy, Chris, he was really transparent.
He was up front with me like, I didn't like what he had to say.
It's the same shit when we have DJ working on our cars.
It's like, I don't want to hear this,
but I'm going to have to do it now.
Or it's going to be 10 times worse, a couple of years
down the road or something like that.
Yeah, it's wild.
How something so small can snowball into something so big.
Well, I appreciate you taking some time to talk about this.
I feel like LML awareness should be something maintenance
awareness in general maintenance awareness on a diesel.
Yeah, I mean, I mean, you're not just buying a truck
because it gets good mileage.
Like there's all sorts of everything.
Really, when you come to maintenance on a diesel on a gas engine,
you're like, yeah, I got to do spark plugs.
I do a fuel filter every once in a while.
Well, nowadays cars, they don't have a fuel filter.
No, it's it's funny that you say that because I had to buy spark plugs
for my car a couple of years ago.
And I'm like, dude, spark plugs are only like eight bucks a spark plug.
Like this fucking cheap.
I know, like what?
That's why I was happy building the car.
I'm like, oh, dude, this this shit's cheap.
And it's like, oh, shit, but compared to the diesel.
That's awesome.
Yeah, diesel price.
There's a diesel tax, the diesel tax on it all.
And I don't I was reading this thing on one of the forums
and this guy had a gas like 66 or a gas 62 or something.
And it was one of the Goodyear six twos.
And he was saying that for him to offset the fuel mileage cost,
he would have to drive his diesel like 500000 miles.
Was that something on Facebook?
Yeah, I saw like he had an Excel document and everything.
Broke it all down.
And it's, you know, it's it's funny to me.
Like, you know, I got into diesel years ago not because of a necessity,
but because I thought it was cool.
It whistled and whistled and rolled cold.
And, you know, it was that I was also 16, 17 years old.
Right. Come on, back in high school.
That's what it was.
Shops, all these these were the thing.
That was a hot ticket, six liter Fords, you know.
So it's like you fast forward till now.
And now I have a diesel pickup out of necessity, right?
A boat, car, stuff that I tow.
Right.
And I say to everybody, man, if I didn't have, you know, the the boat,
then I'd have to tow it.
Fuck, dude, I'd have a half ton pickup gas, not give a shit.
People the same things.
Oh, man, Anthony works at Duramax.
Dude, what truck should I get?
I'm like, don't get one. Don't get one.
You need one. Don't get one.
It's like, what do you do?
Oh, I drive to the city every day to go to work and like get a get in the court.
Yeah. Unless you like, unless you're towing something,
like you have to have one like, yeah, they're cool.
But that coolness wears off when your head gasket should.
The best thing is I got money.
I could pay for it. What do you think?
I got money.
I'm not broke, dude.
It's like, I'm not saying you're broke.
I'm just like helping you out financially.
Like I've seen I've seen guys buy, use trucks and then the trucks
physically cripple them financially.
I feel like we're all guilty of that.
We have whether it be trucks or some toy to some degree.
Hey, man, don't do that. Don't do that.
Or you should get that. I can't afford it.
It's that whole don't touch the fire.
It's hot. I'm putting my hand in the fire.
We're going to feel this out.
Cigarette lighter.
I still got scars on my fingers from that.
So shit, anything?
Any last words that you want to say before we wrap this up?
No, I think we're good.
All right. Well, we appreciate you taking the time.
Thank you very much. Cool. Thank you.
Like we need to start recording that.
And that's a whole other podcast at this point.
We might go to jail if we release that.
About this episode
Reliability talk for LML Duramax owners starts with why fuel economy may be changing, then quickly turns into what a shop tech would do: prioritize the fuel system. The hosts focus on DEF-era reliability, CP4 failures tied to contamination and maintenance, and practical upgrades like lift pumps, finer filtration, and a “system saver” regulator to protect injectors. They also cover winter no-start workarounds, low-fuel pickup issues, and other wear items like sticky turbo vanes and head gasket patterns.
We often get a ton of questions regarding what we would do with necessary upgrades for the LML Duramax. We figured we'd bring in one of the Calibrated Power Shop Techs, Nick Evertsen, to answer that question. Nick has been a GM tech and moved around to independent diesel shops to arriving over at Calibrated Power now. He is taking his decades plus amount of expertise to answer the question, 'Top five reliability upgrades for the 2011-2016 6.6L Duramax.' These trucks are now between 10 and 15 years old(insane to think), and we have the best upgrades that will keep your LML running optimally and for the long haul. Enjoy!
