5 Reliability-Based Upgrades a Shop Tech Would Make To An LML
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!
cab off
"And that was like a full like cab off. [167.6s] And that was like a full like cab off."
“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.
“Cab off” describes a major repair approach where the truck’s cab is removed from the chassis to access components that are otherwise hard to reach. It’s a sign the job is deep—often involving engine/transmission-level work or major driveline repairs—so it’s commonly associated with reliability fixes rather than quick maintenance.
DEF
"“...2011 is the first year of DEF for that platform, and I don't really remember too many DPFEGR problems.”"
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.
DEF (Diesel Exhaust Fluid) is the urea-based liquid injected into the exhaust to reduce NOx emissions in modern diesel trucks. The segment notes that 2011 was the first year of DEF for this platform, which matters because introducing DEF systems often changes the failure patterns (sensors, dosing, tank/lines, and control logic).
DPFEGR
"“...2011 is the first year of DEF for that platform, and I don't really remember too many DPFEGR problems.”"
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.
DPFEGR is a diesel emissions acronym typically referring to an EGR-related system with a differential pressure sensor (D-PF) used to monitor exhaust gas recirculation performance. The speaker says they don’t remember many DPFEGR problems, contrasting it with other issues like the reductant tank. That implies the EGR monitoring/differential pressure side wasn’t the dominant reliability headache during that timeframe.
reductant tank
"I feel like it was more DEF, reductant tank, more related."
A reductant tank is where the truck stores the special fluid it uses to reduce exhaust pollution. That fluid is usually DEF.
A reductant tank stores the fluid used by a diesel’s emissions system to reduce NOx. In most modern systems this reductant is DEF, which is metered into the exhaust for chemical conversion.
no start
"5,000 miles on a truck comes in, tow in, crank, no start, and what do we find?"
“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.
“No start” describes a condition where the engine cranks but does not start, commonly caused by insufficient fuel pressure. On CP4-related failures, the pump may produce little or no pressure, preventing injection.
fuel systems with the metal contamination
"So when you were starting to see these fuel systems with the metal contamination, was GM originally kind of chalking it up?"
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.
Metal contamination in a diesel’s fuel system means debris (often from tank/lines or wear) gets into the fuel and can damage precision components. In high-pressure systems, that debris can score or clog the high-pressure pump and related parts, causing low pressure and hard/no-starts.
granating
"So back then, we didn't see as much granating as we do now, kind of."
“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.
“Granating” here appears to refer to “granulation,” a process where fuel-system debris breaks down into gritty particles. In the context of CP4 failures, it describes how contamination can evolve into fine abrasive material that circulates through the fuel system and accelerates damage.
pump failed
"We just, hey, your pump failed. It came apart. We're replacing your injectors, dropping your fuel tank, cleaning that out."
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.
“Pump failed” refers to a fuel pump failure that can cause loss of proper fuel delivery. On modern diesels, fuel system failures can lead to contamination and misfueling, which then damages other components like injectors. That’s why the shop describes replacing injectors and cleaning the fuel tank after the pump comes apart.
injectors
"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."
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.
Injectors are the components that spray precisely metered fuel into the engine’s combustion chambers. When a diesel’s fuel system fails (like a pump breaking apart), debris and contaminated fuel can damage injectors, leading to poor combustion and drivability issues. The transcript ties injector replacement directly to the pump failure and tank cleaning.
fuel tank
"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."
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.
Dropping and cleaning the fuel tank is a contamination-control step after internal fuel-system failures. If debris from a failing pump contaminates the fuel, simply replacing injectors may not be enough—dirty fuel can keep harming new parts. The transcript explicitly links tank cleaning to getting the customer back on the road.
systemic or a bigger problem
"Third or fourth, like is this a coincidence, or is there something more systemic or a bigger problem here?"
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.
The hosts are discussing whether repeated failures point to a systemic issue rather than isolated coincidences. In reliability work, “systemic” means the underlying cause is likely design-related, process-related, or tied to a common component/condition across many trucks. That’s why they contrast “coincidence” with a broader pattern.
dealer
"I could see that, and that was just one dealer, right? Yeah, yeah. That's happening all over."
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.
CP4s
"We'll fast forward to now for that guy that calls in saying, man, I was on the forum, and [476.9s] CP4s, I'm just deathly afraid to drive this truck anywhere."
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.
“CP4” refers to the CP4 high-pressure fuel pump used on many Duramax diesel engines. When people say they’re “afraid” of CP4s, they’re usually talking about pump failures that can cause hard starting, loss of power, and expensive fuel-system damage.
fuel filter
"but I feel like a big, big thing of it is [500.0s] just fuel contaminants or lack of maintenance, not changing your fuel filter or being the [506.7s] lucky one to get a bad batch of fuel somewhere or something along those lines."
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.
A fuel filter traps debris and water-related contaminants before they reach the high-pressure parts of the diesel fuel system. Skipping filter changes increases the chance that abrasive particles reach sensitive components.
Top tier fuel
"That is a very solid point, and that's what we always advise our customers. [513.4s] Top tier fuel, that will keep your CP4 from failing, and like Chris said, we will go into [521.7s] performance upgrades that will help that CP4, but back at the dealer, you're all stock emissions"
“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.
“Top tier fuel” is a fuel-quality program that sets higher detergent and additive standards than typical baseline fuel. The idea is that better fuel cleanliness helps reduce deposits and contamination-related wear in diesel fuel systems.
stock emissions compliant
"Top tier fuel, that will keep your CP4 from failing, and like Chris said, we will go into [521.7s] performance upgrades that will help that CP4, but back at the dealer, you're all stock emissions [527.6s] compliant."
“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.
“Stock emissions compliant” means the vehicle is configured to meet emissions regulations using the original factory emissions equipment and calibration. The speaker is contrasting this with aftermarket modifications that may not be allowed or may need to be removed for dealer service.
lift pump
"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."
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.
A lift pump is an auxiliary pump that feeds fuel from the tank toward the engine at a steady, lower pressure. On many modern diesels, it helps protect the high-pressure system by ensuring the high-pressure pump isn’t forced to pull fuel under hard conditions.
fuel contaminants
"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."
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.
Fuel contaminants are unwanted particles or water mixed into diesel. In high-pressure diesel systems, contaminants can damage precision components inside the high-pressure pump and injectors, so filtration strategy directly affects reliability.
eight micron
"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."
Microns are a measure of particle size. A lower micron number means the filter can catch smaller particles before they reach the fuel pump.
Micron ratings describe how small particles a filter can remove. The speaker’s point is that a “fast system” can reduce particle size from about eight microns down to about two microns, improving protection for the CP4 pump.
two micron
"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."
Two microns is a very fine filter rating. It means it can trap very small particles that could otherwise reach the high-pressure pump.
Two-micron filtration is very fine filtration for diesel fuel. The speaker uses it to argue that smaller particles are less likely to reach the CP4 pump internals, reducing the chance of pump damage.
water separator
"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."
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.
A water separator is a filter component designed to remove water from diesel before it reaches the high-pressure pump. Water contamination can contribute to corrosion and pump/injector damage, so separating it early improves system durability.
Air Dog
"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."
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.
Air Dog is an aftermarket lift-pump system brand commonly used on diesel trucks. It typically combines fuel supply and filtration to help protect the high-pressure pump from contamination and low-supply conditions.
CP3s
"like, I'm not saying CP3s are the most, you know, like, no, no, but it could happen."
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.
“CP3” refers to a different Bosch high-pressure fuel pump family than the CP4. The speaker contrasts them to note that CP4 failures are the bigger concern, but CP3 failures can still happen.
insurance perspective
"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."
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.
“Insurance perspective” is a reliability budgeting concept: spending on preventative upgrades (like filtration and filter changes) is compared against the cost of a catastrophic failure. It frames upgrades as risk reduction rather than performance gains.
Jamie's LML
"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."
“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.
“LML” is the Duramax diesel engine code used on certain Chevrolet Silverado/GMC Sierra trucks. In this segment, the hosts are talking about reliability issues and upgrades specific to that LML setup, especially around fuel delivery. The context is clearly about a diesel pickup, not a generic diesel concept.
twin kit
"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."
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
"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."
“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.
“Gelled up” refers to diesel fuel thickening when temperatures drop, due to wax crystals forming in the fuel. This can restrict fuel flow and starve the lift pump/high-pressure system, leading to starting and drivability problems. It’s a common winter diesel reliability issue.
prime it manually
"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. ... 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"
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.
Manually priming means forcing fuel through the system to build pressure at the lift pump/filter area so the engine can start. The hosts describe a workaround: if the lift pump fuse pops, you can prime manually and get the truck running again. This is a practical reliability technique for getting home or driving until the fuse is replaced.
sump
"You can add a sump as well with your lift pump with, which is most people do. [733.5s] What's the what's the reason behind that? [736.0s] To get the fuel from the bottom of the fuel tank."
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.
In this context, a sump is a low-point fuel reservoir (often added to the tank area) that keeps usable fuel available for the lift pump. The goal is to pull fuel from the bottom of the tank so the pump doesn’t ingest air when fuel level drops.
stock sending unit
"So as you're improving performance, [744.6s] the stock sending unit will restrict as that pump needs a better diameter hose. [752.5s] OK, the factory, the corrugated hose itself is more restricted"
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.
The sending unit is the factory fuel-level pickup assembly in the tank. The speaker says that as performance is improved, the stock sending unit can become a restriction because the pump needs a better-flowing hose/connection to move enough fuel.
corrugated hose
"OK, the factory, the corrugated hose itself is more restricted than depending on the years. [758.7s] That's why you get a lot of LML guys that will complain that their pumps are loud."
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.
A corrugated hose has ridges that can reduce effective flow area compared with a smoother hose. The speaker claims the factory corrugated hose is more restrictive, which can contribute to pump noise and harder working conditions.
quarter tank issues
"The trucks tend to run into the quarter tank issues a little bit more predominantly. [790.5s] So I like the sumptuous for the fact that it's been a year since I've heard"
“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.
“Quarter tank issues” refers to fuel delivery problems that show up when the fuel level gets down to roughly a quarter tank. The speaker ties it to early days of tying into the factory sending unit, implying the pickup/restriction design can cause air ingestion or reduced flow at low levels.
fuel system saver
"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."
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.
A fuel system saver is an aftermarket device intended to protect a diesel’s high-pressure fuel system and injectors from contamination or failure modes. In this context, it’s described as preventing extra debris/metal from being sent through the system if a component fails.
CP for fails
"Good way to protect your pocketbook. If the CP for fails, it will keep the injectors whole, hopefully."
“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.
“CP” here appears to refer to a component in the fuel system that can fail, and the speaker’s point is that the fuel system saver will keep the injectors from being harmed by what happens during that failure. The transcript implies the device limits how much debris/metal gets carried forward into the injector circuit.
fuel pressure regulator
"Essentially, it's just an upgraded fuel pressure regulator with a reinforced net and a tighter micron, I believe."
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.
A fuel pressure regulator controls the pressure of diesel in the fuel supply line. Keeping pressure in the correct range helps ensure consistent delivery to the high-pressure system and can reduce stress on injectors and related components.
pump and a tank cleaning
"And, you know, we pulled the regulator and do just metal, right? That that second go around was a pump and a tank cleaning."
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.
“Pump and tank cleaning” refers to addressing contamination at the source (the fuel tank) and in the fuel pickup/pump area. If metal or debris is present, cleaning the tank and inspecting the pump helps stop repeat contamination from reaching the regulator, high-pressure system, and injectors.
high pressure system
"It was a whole high pressure system."
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.
On modern diesels, the high-pressure system is the fuel system that pressurizes diesel to very high levels before injection. If components in that system fail, you can get hard-start/no-start issues and drivability problems because the engine can’t deliver the right fuel pressure to the injectors.
2015 LML Duramax twin turbo
"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."
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.
The 2015 LML Duramax is a GM diesel (the LML is the engine code) known for its turbocharged setup and strong aftermarket support. In this segment, the hosts focus on reliability issues tied to the high-pressure fuel system and emissions-related hardware on this specific Duramax generation.
pump was failing
"Regulator was all, you know, metal all over it. The pump was failing."
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.
When the high-pressure pump is failing, it can’t build and maintain the fuel pressure needed for proper injection timing and quantity. That commonly shows up as hard-start/no-start or “no crank” situations, because the engine isn’t getting the correct pressurized fuel.
CP three
"And at that point, we ended up, you know, swapping to a CP three and doing a CP three, 10 mil on that."
“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.
“CP” here refers to a specific aftermarket calibration/performance package designation used by the shop (CP three is a particular version). The speaker contrasts different CP versions (CP three vs CP four) in terms of how often failures show up in their shop.
CP four
"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."
“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.
“CP four” is another version of the same shop’s CP setup designation, discussed here specifically because the tech sees more frequent failures associated with it. The host implies their real-world failure rate is different from what online forums claim.
LBZ
"But like, I've had LBZs with more. Oh, how does that LL?"
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.
LBZ is a GM Duramax engine code (commonly associated with a specific generation of 6.6L Duramax diesels). The host mentions LBZs in the context of comparing failure patterns (like head gasket issues) across Duramax generations.
AC compressor
"If you can move the AC compressor out of your way and you have the right tool set up."
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.
The AC compressor is the component that pressurizes refrigerant for the air-conditioning system. Here it matters because the host says you may need to move it out of the way to access the fuel-system-saver installation area.
diagnostics
"helping walk through diagnostics with a customer ... the total fuel system and they didn't clean everything out appropriately. And they just contaminated the whole new system."
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.
Diagnostics is the process of identifying the root cause of a fault using tests, measurements, and inspection rather than guessing. On diesel fuel systems, diagnostics often includes checking for contamination, pressure issues, and component condition across the entire fuel path. The speaker describes helping a customer walk through diagnostics after a shop repair contaminated the new system.
relief valve
"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."
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.
A relief valve is a safety/control valve that manages pressure in the high-pressure fuel system by allowing fuel to bypass or vent when pressures get too high. If metal debris shows up on the relief valve, it’s a strong sign that the pump or upstream components are shedding particles that then circulate.
snowball effect
"It's a snowball effect downhill at that point. Is it just what's gonna build up on the regulator"
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.
CP3 conversion
"Are we doing a lift pump? [1185.4s] Like when does that CP3 conversion come into the mix?"
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.
A “CP3 conversion” is the broader set of changes needed to install a CP3 pump and make the fuel system work correctly with it. Depending on the truck and goals, it can include additional fuel system components beyond just swapping the pump.
reliability of a CP3
"Like what is your next goal with your truck? [1195.4s] Do you want to produce more power [1199.6s] or have the reliability of a CP3 because old faithful,"
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.
The speaker is framing the upgrade decision around reliability trade-offs: choosing between chasing more power versus investing in a fuel-pump setup (CP3) that’s expected to be more dependable. This is a common shop approach—match the parts plan to the customer’s priorities and risk tolerance.
LB7s
"or have the reliability of a CP3 because old faithful, [1203.1s] I mean, you brought up LB7s, [1205.5s] that's what they had in them."
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.
LB7 refers to an early-generation Duramax diesel engine used in GM trucks. The speaker is comparing earlier LB7 fuel-pump failures—where you might replace just the pump—to later decisions about doing a full CP3 conversion for improved reliability.
common rail
"Like there's a lot of other diesel, common rail vehicles that have CP4s and there's really not CP3 options out there, right?"
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.
Common rail is a diesel fuel system design where fuel is pressurized and stored in a shared “rail,” then delivered to injectors as needed. This allows precise injection timing and pressure control, which is why many modern performance diesels use it. In the transcript, it’s the system context for the CP4/CP3 pump discussion.
500 horsepower
"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,"
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.
67 800 horsepower
"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,"
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.
“67 800 horsepower” appears to be a transcription of a very high horsepower target (likely “678/680” or similar) used to illustrate when CP4 protection is no longer enough. The key point is the host’s threshold logic: higher power demands a CP3 approach for reliability. The exact number is unclear from the transcript, but the upgrade decision is the takeaway.
Dan's diesels
"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,"
Dan’s Diesels is a company that makes aftermarket parts for diesel trucks. The speaker is saying he already had experience installing their stuff.
Dan’s Diesels is an aftermarket brand/supplier of diesel performance and reliability parts. The host mentions it as the first kit he’d installed before moving to the shop, implying it’s a common, easy-to-work-with option.
Worley's kit
"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."
Worley’s kit is an aftermarket upgrade package for diesel trucks. The point here is that installing it takes more work than smaller bolt-on parts.
Worley’s kit refers to an aftermarket diesel upgrade package the shop installs. The speaker groups it with other kits, emphasizing that these upgrades can be more labor-intensive than simpler fuel-system add-ons.
SNS kit
"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."
SNS kit is an aftermarket set of parts for diesel trucks. The speaker is saying it’s the kind of kit that can take a lot of labor to install.
The SNS kit is an aftermarket diesel upgrade package referenced alongside other brands. The host’s comparison suggests it’s part of the same category of reliability/performance kits that may require significant disassembly to install.
fleece
"Worley's kit, an SNS kit, I've even seen this fleece, they're all relative, very nice, they're all very nice kits."
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.
Fleece is an aftermarket diesel parts brand mentioned as another kit option the shop installs. It’s grouped with Dan’s Diesels, Worley’s, and SNS, implying similar “kit” style upgrades aimed at reliability and performance.
bulletproof this thing
"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,"
“Bulletproof” just means making the truck tougher and less likely to break. Here, it’s about doing upgrades so it can reliably last a long time.
“Bulletproof” is enthusiast slang for making a vehicle more resistant to common failures through preventative upgrades and careful setup. In this context, it means spending more now so the diesel truck can run reliably for many years.
CP4 failures
"[1350.5s] Nick, how many CP4 failures would you say you've seen [1353.0s] from you being at the dealer to come into here?"
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.
On GM/Chevy Duramax diesel engines, the CP4 refers to the high-pressure fuel pump used to pressurize diesel for injection. “CP4 failures” usually means the pump wears or sheds metal, which can contaminate the fuel system and damage injectors and other components.
class action lawsuit
"[1382.8s] I think what's crazy is, is like, you know, [1384.5s] now you have like Chevy GM doing this [1388.3s] like whole class action lawsuit with Bosch on the CP4s,"
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.
A “class action lawsuit” is a legal case where many affected customers join together to sue as a group. In this context, it’s being referenced as a response to widespread CP4-related failures tied to Bosch-supplied components.
Bosch
"[1384.5s] now you have like Chevy GM doing this [1388.3s] like whole class action lawsuit with Bosch on the CP4s,"
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.
Bosch is a major automotive supplier that makes components used in many diesel engines, including parts related to high-pressure fuel systems. The transcript ties Bosch to CP4 issues via a lawsuit reference.
recall
"Under recall, that's how they do. [1409.9s] So it's crazy to see how the different manufacturers, [1412.5s] and then you look at Ford,"
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 versus customer pay
"like you're, the dealer's paying. [1454.3s] Yeah, yes, the rate for warranty versus customer pay,"
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.
“Warranty versus customer pay” refers to how labor rates and reimbursement differ when a repair is covered by the manufacturer (warranty) versus when the owner pays out of pocket. This affects how much time a shop can justify for a job and can influence whether certain upgrades get done efficiently during recall repairs.
weak links
"This is where you want to address, these are the weak links to the LML. Agreed."
“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.
“Weak links” is a reliability concept meaning the specific components or subsystems that tend to fail first or cause the most trouble under real-world use. In this segment, the host frames the fuel system as the weak link on the LML platform, implying that targeted upgrades there deliver the biggest reliability gains. It’s a common shop approach: fix the failure-prone bottleneck before chasing everything else.
low side
"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."
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.
On diesel fuel systems, the “low side” generally refers to the lower-pressure portion that moves fuel from the tank through the filter and up to the high-pressure system. Problems here (like restricted flow or weak supply pressure) can starve the high-pressure side and lead to poor running or accelerated wear. The host groups “low side” issues with “high side” issues as the key reliability targets.
high side
"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."
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.
On diesel fuel systems, the “high side” refers to the higher-pressure portion that pressurizes fuel for injection into the cylinders. If the high-pressure side has issues, it can cause misfueling, drivability problems, and potential damage to precision components like injectors. The host’s reliability advice is to address both low-side supply problems and high-side pressure/injection problems.
vanes will stick in the turbo
"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."
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.
This refers to sticking turbocharger vanes (often in a variable-geometry turbo). When the vanes don’t move freely, boost control can be inconsistent and the turbo may need replacement if it can’t be freed.
burnouts
"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."
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.
Burnouts are repeated wheel-spin events that can raise exhaust heat and load. In this context, the host suggests that doing a couple of burnouts after storage can help free sticky turbo vanes temporarily.
head gaskets
"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."
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.
A head gasket is the sealing layer between the engine block and the cylinder head. If it fails, combustion gases and/or coolant can leak where they shouldn’t, which can quickly lead to overheating, loss of coolant, and hard-to-diagnose drivability issues. In this segment, the host says the LLY and LML Duramax platforms had recurring head gasket failure patterns.
deck clearance
"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."
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.
Deck clearance is the measured gap/relationship between the engine block “deck” surface and the cylinder head when assembled or during inspection. Shops check it to confirm the engine will seal correctly and that the head gasket thickness and machining/flatness are appropriate. The host says he “would check the deck clearance” before reassembly.
head bolts
"If it passed, it went back together with new head gaskets, new head bolts, customer was on their way."
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.
Head bolts clamp the cylinder head to the engine block, maintaining the sealing force on the head gasket. When a shop replaces head gaskets, they often also replace head bolts because the bolts can stretch or lose clamping load after removal. The host pairs “new head gaskets” with “new head bolts,” indicating a proper reseal procedure.
timing belts
"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."
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.
A timing belt synchronizes the crankshaft and camshaft so the engine’s valves open at the correct time. Many engines require periodic replacement; if it fails, valve timing can be thrown off and in interference engines it can cause severe internal damage. The host mentions timing belts as part of the maintenance that may be needed around higher mileage (like near 100,000 miles).
glow plugs
"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."
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.
Glow plugs are the small heating elements in a diesel engine that warm the combustion chambers to help the engine start and run smoothly, especially when cold. On many modern diesels, worn or failing glow plugs can also lead to harder starting and can contribute to bigger problems if heat and combustion aren’t managed correctly.
head gasket jobs
"And we've had glow plug jobs turned into head gasket jobs"
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.
A head gasket is the seal between the engine block and the cylinder head; when it fails, coolant and combustion gases can mix, causing overheating, loss of compression, or other serious symptoms. The host is warning that glow-plug-related issues on these diesels can sometimes escalate into head gasket repairs, which are far more expensive.
pull the heads
"And it's like, hey, man, we need to pull the heads. [1809.7s] You didn't tell me this."
“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.
“Pulling the heads” means removing the cylinder head(s) from the engine block. This is typically done for major repairs like head gasket replacement, and it requires careful reassembly and often new sealing components. It’s labor-intensive, so shops usually manage expectations on time and cost.
diesel tax
"Yeah, diesel price. There's a diesel tax, the diesel tax on it all."
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.
“Diesel tax” is a shorthand for the extra taxes/fees that can apply specifically to diesel fuel compared with gasoline. In practice, it affects the cost-per-mile and can make diesel ownership feel more expensive even if the truck gets better fuel economy.
fuel mileage
"And he was saying that for him to offset the fuel mileage cost, he would have to drive his diesel like 500000 miles."
“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.
“Fuel mileage” refers to how efficiently a vehicle uses fuel, typically expressed as miles per gallon (MPG). It’s central to the diesel-vs-gas cost discussion because diesel trucks often have better MPG but can face higher fuel taxes or higher purchase prices.
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