When it comes to diesel engines there have been many outstanding improvements and upgrades from the OEM over the years. Turbocharging, intercooling, common rail injection, variable geometry turbochargers and more. Among the list of awesome technology that was developed you might have noticed, I didn't mention the CP4 injection pump. Well I assure you, there is a reason for that. So what is a CP3, or CP4, CP4.1 or even a CP4.2? These are all designations for common rail injection pumps. They are gear driven pumps that pressurize diesel fuel which is then fed to the injectors and then to your engine.
Lets give you some back story. As early as 2001 for GM and 2003 for Dodge adopted the venerable Bosch CP3. This pump was a stalwart unit for GM Duramax trucks for a decade and standard issue for Dodge/Ram Cummins powered trucks for 15 years. So why ruin a good thing? Emissions standards and cost. The CP3 is a heavy, solid pump with 3 pumping elements instead of two. It utilizes an offset cam with a polygon and a single-bucket that houses an actuator. This polygon is rotated elliptically to build fuel pressure. The CP3, can be modified to a stroker pump commonly in sizes of 10mm, 12mm and 14mm or even used in a twin-pump setup with a second belt driven CP3 capable of making enough fuel pressure and volume to support beyond 1000whp.
The Injection Pump Graveyard
CP4 pumps of different variations have been in use by GM Duramax trucks beginning with the introduction of the LML Duramax in 2011, Ford Powerstroke trucks since the adoption of the 6.7 Powerstroke, Ram tried it out for 2 model years in 2019-2020 (that went pretty badly), Ram/Jeep EcoDiesel powered vehicles and many european market vehicles make use of CP4 injection pumps. CP4 pumps are constructed of aluminum and utilize a 2 element pumping design. This design, is their fatal flaw. By making use of an aggressive camshaft with a bucket that features a roller that rides on the cams lobes. (think roller cam/lifter combo in a gas engine)
CP4.2 and CP3 Injection Pumps
CP4's may be distinguished by their nomenclature which relates to their design. CP4.1 and CP4.2 with the predominant difference being the number of pumping elements. The LML, early 5th Gen Cummins, and 6.7 Powerstroke make use of a CP4.2. The CP4 does do the job of supplying high pressure diesel fuel but it sadly has an unacceptable rate of failure usually before the 100,000 mile mark which leaves owners both stranded on the side of the road and out $10,000 for a replacement fuel system. The aggressive camshaft and lobe design WILL result in erosion of the cam material resulting in debris (seen below as metal shavings) to begin moving through the fuel system. As this process continues and the wear intensifies the rollers will actually begin to skid across the now worn flat lobes. When the CP4.2 gives up the ghost, it REALLY gives up the ghost. Think glitter bomb in your fuel system. This means the entire system has to be removed and replaced as the contamination from your pump failure will have trashed the system from front to rear.
CP4.2 pump debris
Roller wear and camshaft erosion So what can you do about this absolute nightmare under the hood. Some folks will claim fuel lubrication like Hot Shot's Secret EDT or similar fuel treatments are helpful and they may be a band-aid but they cannot eliminate the design flaw in the CP4.2. What you can do to stop the damage from this grenade going off in Ford trucks is utilize the S&S Diesel Motorsport CP4.2 Disaster Prevention Bypass Kit.
S&S Diesel Motorsport CP4.2 Disaster Prevention Bypass Kit 2011-2022 Ford 6.7 Powerstroke
The Disaster Prevention Bypass Kit will protect your injectors, rails, lines and fuel tank from CP4 debris. (did we mention that glitter grenade goes everywhere?) This kit uses a 9 micron return fuel filter to help capture any debris and a fuel supply split off distance of 25 inches from the CP4. For the LML Duramax guys, S&S has a solution for you as well. We utilize their LML CP3 Conversion Kit to help remedy the CP4.2's root problem of being an absolute engineering failure. This replacement kit does not require any custom tuning, maintains all factory emissions equipment and is 50 state legal as it has a CARB EO number on file for California residents.
S&S Diesel Motorsport LML CP3 Conversion Kit (2011-2016 GM 6.6 Duramax)
Last but certainly not least for the unfortunate ones that received a 6.7 Cummins engine with a CP4.2 installed, S&S hasn't forgotten you. They also produce a CP3 conversion for 2019-2020 Ram 6.7 Cummins as well. Again this fixes the CP4.2 problem by allowing you to safely place it in the dumpster. As with the LML CP3 conversion kit this is a No Tune Required kit that is 50 state legal.
S&S Diesel Motorsport CP3 Conversion for 2019-2020 Ram 6.7 Cummins
The last item we will leave you with is a video by Luke from S&S Diesel Motorsport helping to give you some visuals and explain CP4 pump failure.
S&S DIESEL MOTORSPORT CP4 FAILURE VIDEO
- Overland Industries