Best CP3 Conversion Kit for LML Duramax: Brands Comparison

The Bosch CP4.2 high-pressure pump on your 2011–2016 LML Duramax is a common failure point that can contaminate the entire fuel system with metal debris and cost up to $12,000 in repairs. We break down the top conversion options so you get reliable fueling without the risk.

EGR Performance CP3 Conversion Kit stands out as the best all-in-one hardware solution for 2011–2016 LML Duramax trucks. It delivers a complete vehicle-specific package including high-pressure lines, preformed hoses, fittings, a mounting adapter, dosing-injector distribution block, low-pressure feed line, and installation hardware.

S&S Diesel Motorsport and Fleece Performance offer strong emissions-compliant and OEM-style alternatives, but EGR Performance provides maximum hardware value at a competitive price point without forcing you to hunt for parts separately.

Picking the best CP3 conversion kit for LML depends on how you use your truck. A daily driver does not need the same setup as a truck built for towing or more power. The kit also needs to fit the 2011-2016 LML fuel system and work with the rest of the truck without creating new problems.

In this guide, we compare the main CP3 conversion kit options based on fitment, included hardware, tuning needs, emissions requirements, pump choice, and intended use. This should make it easier to choose the right CP3 conversion for LML Duramax without paying for parts you do not need.

Which LML CP3 Conversion Kit Is Best?

EGR Performance provides a complete, budget-friendly hardware package for 2011–2016 LML trucks, S&S Diesel Motorsport delivers a 50-state CARB-compliant option ideal for emissions-intact daily drivers, and Fleece Performance features OEM-style routing and molded hoses designed to pair seamlessly with aftermarket lift pumps and high-horsepower upgrades.

There is no single best CP3 conversion kit for LML trucks. The right selection will depend a good deal on your application and on just what you may be hoping for from your fuel system.

An everyday stock truck has different demands compared to a build running a lift pump, larger injectors, and various other fuel system upgrades.

For a stock LML Duramax, a standard CP3 setup is the ideal starting point, whereas pump sizing becomes critical when building for higher fuel flow.

It is also wise to verify what's included before purchasing, as some CP3 conversion kits for LML supply the pump while others are sold as hardware-only packages.

Why Do LML Duramax Owners Convert From CP4 to CP3?

LML Duramax owners convert from the failure-prone factory CP4 pump to the robust CP3 to prevent catastrophic, multi-thousand-dollar fuel system destruction caused by pump metal debris.

Before committing to a CP3 conversion, it is also worth looking at the common fuel-system problems on the LML. Our guide to common LML Duramax problems covers the CP4 pump and other issues owners should watch for.

The main reason for a CP4 to CP3 conversion is reliability. The factory CP4.2 pump can fail and send metal through the fuel system. When that happens, the damage can extend beyond the pump to the injectors, fuel rails, and lines. The repair can become expensive once the whole system needs to be cleaned or replaced.

A CP3 conversion for LML Duramax trucks replaces the factory CP4 setup with a CP3 pump. Many owners do the swap before the CP4 fails, especially if they plan to keep the truck for years.

There is another reason to consider the swap. A stock CP4 has limited fuel capacity for higher-power builds. If you plan to add larger injectors or other performance parts, a CP3 pump for LML Duramax gives you more room to build the fuel system around those upgrades.

For a stock truck, the main benefit is having a different high-pressure fuel pump setup. For a modified truck, the extra fuel capacity can become just as important.

How We Ranked the Best CP3 Conversion Kits for LML

The evaluated LML CP3 conversion kits, EGR Performance, S&S Diesel Motorsport, and Fleece Performance, provide precise 2011–2016 LML fitment and ninth-injector support without requiring immediate tuning, with the EGR Performance kit offering the highest overall value, S&S delivering 50-state CARB legality with top hardware, and Fleece providing reliable, factory-style lines.

We compared each LML CP3 conversion kit based on what you get for the price and how well it suits the truck you are building.

• Fitment: Will the part fit a 2011-2016 LML Duramax without modification?
• Tuning: Does this require any tuning, or will factory calibration suffice?
• Emissions: Does this have a CARB Executive Order number?
• Included parts: What fuel lines, fittings, hoses, brackets, and pump options come with the kit?
• Installation: Clean routing and proper integration with the factory fuel system matter during a CP4 to CP3 conversion.
• Value: The price needs to make sense for what comes with the kit and how you plan to use the truck.

A kit that works well for a stock daily driver may not be the right choice for a high-power LML. That is why we looked at the complete setup rather than judging each CP3 conversion kit for LML Duramax on price alone.

If you are planning other fuel-system upgrades at the same time, you can also see the LML Duramax performance parts available for 2011-2016 trucks.

Best CP3 Conversion Kits for LML Duramax

The best LML CP3 conversion kits, EGR Performance, S&S Diesel Motorsport, and Fleece Performance, cater to different buyer priorities, offering a high-value hardware package for budget-conscious builders, a 50-state CARB-compliant premium setup for strict emissions states, and an ultra-clean, OEM-style installation with flexible high-horsepower upgrade paths, respectively.

The three kits below take slightly different approaches. One focuses on getting the hardware you need in one package, while the others put more emphasis on emissions compliance, factory-style fitment, or future fuel-system upgrades.

EGR Performance CP3 Conversion Kit: Best Value Hardware Option

For owners who want the main conversion parts in one package, EGR Performance CP3 conversion kit is a practical choice. It fits 2011-2016 LML Duramax trucks and includes the main lines, fittings, hoses, mounting adapter, dosing-injector distribution block, and other hardware needed for the conversion.

CP3 Conversion Kit for 2011-2016 LML Duramax

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You can check EGR Performance CP3 conversion kit for the exact fitment and included parts.

• CP3-to-rail high-pressure line
• Feed and return fittings
• Preformed feed and return hoses
• Mounting adapter
• Dosing-injector distribution block
• Low-pressure feed line
• Installation hardware

The kit does not include the CP3 pump, so you can choose the pump that suits your build. That can make sense if you already have a pump in mind.

Best for: Stock trucks, mild builds, and owners who want the conversion hardware without buying a bundled pump.

Pros:

• Designed for 2011-2016 LML Duramax
• Complete plumbing and mounting hardware
• Includes the dosing-injector distribution block
• 1-year warranty

Cons:

• CP3 pump is not included
• Installation instructions are not included
• Tuning and emissions requirements should be checked before installation

Bottom line: If you mainly need the hardware for a CP3 conversion for LML Duramax, EGR Performance gives you the main pieces in one kit.

S&S Diesel Motorsport LML CP3 Conversion: Best Emissions-Compliant Option

S&S Diesel Motorsport is a strong choice for owners who want to keep the factory emissions setup. Its emissions-compliant LML conversion is aimed at street-driven trucks and offers a no-tune configuration.

Best for: Daily drivers, emissions-equipped trucks, and owners looking for a CARB-compliant option.

Pros:

• 50-state CARB-compliant option
• No tuning required for the applicable configuration
• Designed to retain factory emissions equipment
• Separate options for performance applications

Cons:

• Higher price
• You need to select the correct version for your truck

The main thing to watch is the configuration. The emissions-compliant kit and competition versions are built for different uses. If you need a CP3 conversion LML setup for a street truck, make sure you select the emissions-compliant version.

Fleece Performance LML CP3 Conversion: Best OEM-Style Option

Fleece Performance focuses on clean installation and factory-style fitment. Its CP3 conversion kit for LML Duramax uses molded feed and return hoses, high-flow fittings, and a valley feed line.

Best for: Owners who care about clean hose routing and want room for future fuel-system upgrades.

Pros:

• OEM-style hose routing
• Bosch CP3 options
• Hardware-only option available
• 10mm stroker option available
• No-tune configuration available

Cons:

• Higher price
• Lift-pump pressure needs to match the kit requirements

For a stock truck, the standard setup is usually enough. If you plan to add larger fuel-system parts later, the 10mm CP3 option gives you more room to grow.

Brand Comparison

Which CP3 Conversion Kit Is Best for Your LML Build Goal?

Selecting the ideal LML CP3 conversion kit depends on your primary build goal: S&S and Fleece suit daily drivers needing 50-state emissions compliance, EGR Performance and Fleece stroker kits cater to high-horsepower builds, S&S and Fleece excel in heavy towing under sustained loads, and EGR Performance provides the best budget-friendly complete hardware value.

Your truck's current setup should guide the decision. A stock daily driver, a work truck, and a modified LML can all use a CP3 conversion, but they may need different pump options and hardware.

Stock Daily Driving

For a mostly stock LML, there is little reason to jump straight to a large performance pump. S&S Diesel Motorsport and Fleece Performance both offer stock-oriented options with factory-style operation.

If keeping the original emissions system matters, check the exact emissions certification and tuning requirements before ordering.

More Power Down the Road

Planning bigger injectors or other fuel-system upgrades changes the picture. A larger CP3 can give the truck more fuel capacity for future modifications.

Fleece offers a 10mm option for higher-demand builds. EGR Performance CP3 Conversion Kit for LML is another route if you want to choose the CP3 pump separately.

If your main build goal is supporting high-horsepower tuning alongside a high-flow CP3 pump, optimizing fuel delivery is only half the equation.

To effectively lower exhaust gas temperatures (EGTs) and clear the extra exhaust flow from aggressive fueling tracks, pair your pump upgrade with dedicated components from our LML full delete kits.

Heavy Towing and Work Trucks

A truck that regularly pulls heavy loads needs steady fuel delivery. In this case, the pump is only part of the setup. Your lift pump, fuel pressure, and the rest of the fuel system need to work together.

S&S Diesel Motorsport and Fleece Performance are worth considering for this type of use, depending on the exact configuration.

Keeping the Cost Under Control

If you already have a CP3 pump or want to select one yourself, a hardware-only kit can make more sense than buying a complete package. EGR Performance includes the main conversion hardware, including the high-pressure line, mounting adapter, hoses, fittings, and dosing-injector distribution block.

Before buying a CP3 conversion kit for LML Duramax, check the pump size, tuning requirements, emissions status, and fuel-supply pressure. Those details matter more than simply choosing the most expensive kit.

What to Check Before Buying an LML CP3 Conversion Kit

Before buying an LML CP3 conversion kit, you must verify 2011–2016 engine fitment, choose between full pump or hardware-only packages, check tuning and CARB emissions compliance, and confirm compatibility with your specific aftermarket lift-pump feed pressure.

Before ordering a CP3 conversion kit for LML Duramax, make sure the kit fits your truck and works with the rest of your fuel system.

• Check fitment: The kit should be made for your 2011-2016 LML Duramax. Kits made for other Duramax models may use different parts.
• See what comes with it: Some kits include the CP3 pump, while others only supply the conversion hardware. The EGR Performance LML CP3 conversion kit lets you choose the pump separately.
• Check tuning: A stock-style setup may work with the factory calibration. Larger pumps and performance builds can have different tuning requirements.
• Check emissions: If emissions testing applies to your truck, look at the kit's current compliance status before ordering.
• Match the lift pump: A lift pump can help keep fuel delivery steady, but its pressure must stay within the limits of the CP3 setup.
• Plan for later upgrades: If bigger injectors or a larger turbo are in your plans, choose a pump that can handle those changes.

A lower-priced CP3 conversion kit LML may not be the cheaper option once you add the pump and any missing hardware. Look at the complete setup before comparing prices.

LML CP3 Conversion Installation and Ninth-Injector Considerations

Installing an LML CP3 conversion kit is a complex, 12-to-16-hour professional job that requires meticulous engine valley teardown, proper ninth-injector distribution block integration for emissions regeneration, and careful line routing to ensure long-term reliability.

A CP3 conversion LML Duramax is not a quick pump swap. The pump sits deep in the engine valley, so getting to it means removing intake plumbing and other fuel-system components first.

The installation usually involves:

• Removing the factory CP4 pump
• Installing the CP3 and mounting adapter
• Connecting the high-pressure rail line
• Routing the feed and return lines
• Connecting the low-pressure fuel supply
• Connecting the ninth-injector dosing system

The ninth injector is easy to overlook. The 2011-2016 LML uses a fuel injector in the exhaust system to add fuel during DPF regeneration. A proper CP3 conversion kit for LML Duramax needs to account for this system and provide the required lines and fittings.

EGR Performance kit includes a dosing-injector distribution block along with the related fuel lines. That helps keep the factory regeneration fuel supply connected during the LML CP4 to CP3 conversion.

This is a job where having the right parts matters. Professional installation is recommended, especially if the truck has additional fuel-system or performance upgrades.

FAQs

Does an LML CP3 conversion require tuning?

Not always. Some kits work with the factory calibration. Larger pumps and performance builds may need custom tuning.

Do I need a lift pump with a CP3 conversion?

Not necessarily. A lift pump can help with fuel supply, but its pressure must match the CP3 setup.

Can I daily drive an LML after a CP3 conversion?

Yes. A properly installed CP3 conversion can work well on a daily-driven LML.

Which CP3 conversion kit is best for towing?

S&S and Fleece are good options for towing. The pump size and fuel supply also need to match the truck.

Does a CP3 conversion increase horsepower?

A CP3 conversion removes the stock CP4's 500 hp limitation. Properly fueled builds routinely reach 650-800+ hp with the same turbo and injectors. The swap itself does not add much power. It mainly improves fuel-system reliability and gives you more fuel capacity for future upgrades.

How long does an LML CP3 conversion take to install?

It is a fairly involved job. Professional installation can take around 12 to 16 hours.

What happens if the LML CP4 pump fails?

A failed CP4 can send metal through the fuel system. The injectors, rails, lines, and other components may then need to be cleaned or replaced.

Is a CP3 conversion worth it on a 2011-2016 LML Duramax?

For many owners, yes. It can reduce concern over the factory CP4 and gives the truck more room for future fuel-system upgrades.

Is a CP3 conversion better than a CP4 disaster-prevention kit?

They solve the problem in different ways. A CP3 conversion replaces the CP4, while a disaster-prevention kit helps contain damage if the CP4 fails.

What is the difference between a stock CP3 and a 10mm CP3?

A stock-style CP3 is suitable for standard fuel demands. A 10mm CP3 can supply more fuel and is better suited to higher-power builds.

Can I keep factory emissions equipment with a CP3 conversion?

Yes, with an emissions-compliant kit. Check the specific kit's certification and your local requirements before buying.

What lift-pump pressure is safe with an EGR Performance LML CP3 kit?

Check the pressure limit for the CP3 pump you plan to use. The lift pump should stay within the pump and fuel-system specifications.

Final Verdict: Which Is the Best CP3 Conversion Kit for LML?

The right LML CP3 conversion kit depends on what matters most for your truck.

EGR Performance: Best Value / Best Hardware Package

The EGR Performance LML CP3 Conversion Kit is a solid choice if you want the main conversion hardware in one package. The CP3 pump is selected separately.

S&S Diesel Motorsport: Best Premium / Emissions-Compliant Pick

S&S is a good fit for street-driven trucks that need an emissions-compliant setup. Its applicable LML kit offers 50-state CARB compliance and a no-tune configuration.

Fleece Performance: Best OEM-Style Fit-and-Finish

Fleece focuses on clean installation and factory-style routing. Its 10mm CP3 option also gives higher-power builds more fuel capacity.

For the final choice, compare the pump, including hardware, tuning needs, emissions requirements, and how you use the truck.

About the Author - Mark Peterson

With 20 years under the hood of heavy-duty diesel trucks, I've seen every wrench turn and sensor failure imaginable. My mission is to help Powerstroke, Cummins, and Duramax owners push their engines to the limit. I don't just review parts - I provide field-tested solutions based on two decades of diagnostic data.

More Reading

• Lml Injector Upgrade
• Convert LML Duramax CP4 Injection Pump to CP3
• How to Prevent The Dreaded LML CP4 Injection Pump Failure