Fleece Performance 11-16 GM 2500/3500 Duramax LML CP3 Conversion Hardware Kit w/o Pump

If you own a 2011-2016 Silverado or Sierra 2500/3500 with the 6.6L LML Duramax, you already know the worry: the factory CP4.2 high-pressure pump can fail without warning and send metal through the whole fuel system. This Fleece Performance FPE-LML-CP3-NP kit contains every adapter, line and fitting needed to bolt a Bosch CP3 in place of the CP4. It does not include the pump itself, so you can supply the CP3 you want to run.

What the CP3 conversion does on an LML Duramax

The LML came from the factory with a CP4.2. The kit swaps it for the LBZ/LMM-style CP3, the pump used on 2006-2010 Duramax trucks. Fleece's kit supplies the CP3-to-block adapter, a new pump-to-rail high-pressure line, high-flow CP3 feed and return fittings, molded feed and return hoses, a cascade block that holds the overflow valve and fuel temperature sensor, the dosing injector distribution block and lines, a regulator (FCA) extension harness, a valley low-pressure feed line for aftermarket lift pumps, and the hardware. Per Fleece, a stock CP3 needs no FCA table changes after the swap.

Why owners convert

• A CP4 failure usually contaminates the rail, injectors and lines, and the repair means replacing most of the fuel system.
• Low rail pressure, often logged as P0087, can point to a CP4 that is wearing out, along with long cranking or a crank-no-start.
• Glitter in the fuel filter or on the regulator screen is the sign that internal wear has already started.
• Owners who plan to add more fuel later want the extra capacity a CP3 has over a CP4.

How to confirm what you need before buying

If the truck is running, log rail pressure desired versus actual with a scan tool before you order. If the CP4 has already failed, pull the high-pressure regulator and look for debris. Fleece says that if you find any, replace the regulator (GM 12611872), the injector return lines and the check valve as well. A failed pump means the whole system needs a cleanout, not just a pump swap. Because the LML has an Allison 1000 behind it, our Allison 1000 limp mode guide helps you rule out transmission faults if the truck is also dropping into limp mode.

Fitment

Fleece lists this kit for 2011, 2012, 2013, 2014, 2015 and 2016 Chevrolet Silverado and GMC Sierra 2500/3500 with the 6.6L LML. It is CARB EO D-834-1, so it is legal in all 50 states. It accepts an LBZ/LMM-based Bosch CP3. A pump such as the Fleece 06-10 LBZ/LMM CP3 is the usual starting point. If you would rather buy the pump and hardware together, see the kit with a new CP3 or the kit with the 10mm stroker CP3. Not sure your truck is an LML? Send us the year and VIN before you order. You can also browse Allison 1000 Duramax parts for the rest of the drivetrain.

Install notes

• Fleece rates the job at 12-14 hours. You will need to drain the coolant, pull the fan and remove the intake, the cold-side charge pipe and the old lines.
• Move the drive gear and nut from the CP4 to the CP3, with the pump held in soft jaws. Torque the gear nut to 75 ft-lb. The CP3 does not need to be timed to the camshaft.
• Oil the adapter O-rings and torque the adapter bolts to 18 ft-lb. Do not use the bolts to pull the pump into the block.
• Fit the new high-pressure line at 28 ft-lb at the pump and 22 ft-lb at the rail. Move your existing fuel temperature sensor to the cascade block.
• Prime the fuel system. Then run a DPF regeneration with a scan tool to purge air from the hydrocarbon dosing injector and its lines.
• With a lift pump, keep feed pressure at the CP3 within Fleece's limit for your pump. That is 5-6 psi with their stock CP3 and 2 psi with the 10mm stroker. Higher pressure can cause surging. The LML PowerFlo in-tank pump needs a lower-rate spring when paired with the stroker.

Does this kit come with a CP3 pump?

No. FPE-LML-CP3-NP is the hardware only: adapter, high-pressure line, fittings, hoses, cascade block, dosing lines, FCA extension harness and bolts. You supply an LBZ/LMM-based Bosch CP3, or you can order the version that includes a new pump.

Will it fit my 2016 Sierra 2500 Duramax?

Yes, if it has the 6.6L LML. Fleece lists 2011-2016 Chevrolet Silverado and GMC Sierra 2500/3500 LML trucks. It does not fit the 2017-up L5P or earlier LMM trucks. If you are unsure, send us your VIN.

Do I need a tune after switching to a CP3?

Fleece states that no FCA regulator table changes are needed when converting to a stock CP3 with this kit. If you run a stroker pump or a lift pump above the recommended feed pressure, the FCA tables may need to be adjusted.

My CP4 already failed. Is this kit enough?

Not by itself. A failed CP4 usually spreads debris downstream. Fleece recommends inspecting the high-pressure regulator and replacing the regulator, injector return lines and check valve if debris is present. Many trucks also need injectors and a full system flush.

How long does the install take?

Fleece estimates 12-14 hours. The job includes draining coolant, removing the fan and intake, swapping the drive gear onto the CP3, and finishing with a fuel prime and a scan-tool DPF regeneration to bleed the dosing injector.

Is the conversion emissions legal?

Yes. The kit carries CARB Executive Order D-834-1, so it is 50-state legal on the listed LML trucks.

• Allison 1000 Limp Mode Causes
• Allison 1000 Transmission Service Guide
• Allison 1000 Fluid and Filter Service Specs