2007.5-2010 GMC Duramax LMM Injection Pumps

Where the CP3 lives on a Sierra HD LMM

The Bosch CP3 bolts into the valley between the cylinder heads and is driven off the cam gear. It is the only pump the Sierra has: the mechanical pump at the back of the CP3 draws fuel up from the tank, and the pump body then raises that fuel to 26,000 psi for the rails. That arrangement held for every Duramax from 2001 through 2016, and the LMM carried the CP3 through the end of 2010 before the 2011 LML switched to a CP4. A regulator on the pump controls output pressure, a bracket locates the pump, and inlet fittings, feed lines and hoses connect it to the rest of the system.

What fails and why

Work the list in order rather than starting with the most expensive part. Low rail pressure, P0087, can come from a clogged filter, an air leak on the supply side, a failing CP3, a bad pressure regulator or worn injectors, and it typically shows up first when the Sierra is towing in heat: reduced power, a limp on acceleration, high EGT. The practical first step is to replace the filter on schedule and inspect the filter-head seals and primer, because micro-cracks and a cracked primer let air into the supply and produce hard starts and long cranks that read like a pump fault. There is also a plain supply limitation to be aware of. With no lift pump from the factory, the CP3 sometimes has a hard time keeping up, which a towing or tuned truck feels as hesitation, sluggish acceleration and low-rail codes.

Stock replacement vs. upgrade

Once a test actually implicates the pump, stock-flow CP3s are cataloged for the LMM in both remanufactured and brand-new form, and that is the repair for a Sierra that needs to go back to work. The regulator is the cheaper part of the same conversation, and regulator kits, bolts and a billet rear bracket let you refresh everything that mounts and meters the pump in one go. Going beyond stock is a volume decision, not a repair: 10, 12 and 14 mm stroker CP3s and dual-fueler twin-pump kits exist for trucks whose injectors and calibration already demand more fuel than one stock pump delivers. Support any of that with a frame-mounted lift pump and extra filtration, which steadies supply under load and looks after the CP3 and the injectors, and hold the pressure it feeds the CP3 to roughly 10 psi.

What we carry

PPE covers the conversion hardware for a Sierra: dual-fueler twin pump kits with or without the pump, twin pump installation kits, CP3 feed line kits in 3/8 and 1/2 inch, CP3 inlet fittings and the bracket-to-block O-ring. Pumps come from Dynomite Diesel in new stock, remanufactured stock and new 12 mm stroker form, S&S Diesel Motorsport high-pressure pumps, a remanufactured CP3 from BD Diesel, a reverse-rotation Sportsman CP3 from Exergy Performance, and a remanufactured stock-replacement CP3 from XDP. Merchant Automotive supplies the fuel pressure regulator and regulator kit, regulator bolts, the billet CP3 rear bracket and the pump inlet and return hoses, while Fleece Performance Engineering lists a CP3 adapter and Exergy adds a CP3 rear outlet fitting and plug kit.

Fitment notes

This page is the GMT900 Sierra HD with the LMM, in WT, SLE or SLT trim; the 2007 Classic Sierra HD is the earlier GMT800 body with the LBZ. Stock-flow pumps for your truck are listed 2006-2010, while brackets, O-rings, feed line kits and fittings commonly cover 2001-2010 or 2001-2016 Duramax applications. Some pumps in this aisle are Cummins-based and listed for the 6.7L rather than the 6.6L, so read the years and engine on the listing. If a lift pump is part of the project, your box length decides the tank you are plumbing into. Verify by VIN or use the fitment checker on the product page.

Frequently asked questions

How do I tell a failing CP3 from a bad fuel pressure regulator?

You test rather than guess, because both land on the same low rail pressure code. Rule out the filter and any air leak at the filter head and primer first, then check rail pressure against what the ECM is commanding. Balance-rate and return-flow testing on the injectors keeps them from being blamed for a pump or regulator fault, and vice versa.

What is a dual-fueler kit, and does my Sierra need one?

It adds a second CP3 so two pumps share the job of supplying the rails. It is for trucks that have already outgrown one stock pump through larger injectors and matching calibration, not something a stock Sierra benefits from. The kits are sold with the pump or as installation hardware only if you are supplying your own.

Will these pumps fit a 2011 Sierra 2500HD Denali?

No. The HD trucks were heavily revised for 2011, and that is when the LML engine with its CP4 pump arrived and when the Sierra Denali HD trim appeared. A Sierra wearing a Denali HD badge is not an LMM truck, so shop the LML pages for it. Everything here is for 2007.5 through 2010.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.