air intake

BACK TO THE CP3 - BD CP3 Conversion Kit and Why You Need It

Technology is constantly moving forward, and when changes are introduced, they are meant to be improvements. Every now and then, however, going back is a good idea. A perfect example can be found with the Bosch CP3 being replaced with the CP4. Now, Dodge is recalling their CP4s.

What is the issue with the CP4 and what options are there for those with a CP4 on their 2019 and 2020 Cummins engine?

Up until 2019, the common rail Cummins engine came equipped with the Bosch CP3, at which point Cummins replaced it with the CP4. While changes are generally intended to be upgrades, this was anything but. In fact, switching to the CP4 resulted in numerous pump failures and considerable damage to the entire fuel system. The result? Tens of thousands of dollars in repair costs and an urgent plea for a reversal of course.

For everyone with a CP4 wanting to go back to CP3 – which should be everyone – BD Diesel offers the CP3 conversion kit for the 2019 and 2020 model year Cummins.

What went wrong with the CP4? 

The CP4’s aluminum body is 25% smaller than the CP3. It is quite fragile, and when it implodes, metal filings are released, which are then pumped through the entire fuel system of the vehicle. This results in the failure of not only the pump but also the injectors and every fuel line of the truck. Owners are then faced with the expense of cleaning the tank and then replacing every hose or line, the injectors and, naturally, the pump.

While that is clearly a major problem on its own, there are additional performance problems. As mentioned above, the CP4 pump is 25% smaller than the CP3. To compensate for this, Cummins adjusted the drive ratio on the gear, cranking it up and overdriving the pump slightly to keep pace with the engine in stock form.

The BD Diesel install kit puts that overdrive to good use, allowing you to put in a CP3 pump while taking advantage of the overdrive of the gear ratio. The result is enough fuel to accommodate any and all performance or aftermarket accessories installed on your truck.

UPDATE: Chrysler is now offering potential reimbursement for these failures. Apply here: 

Using the kit, you can replace the problematic CP4. Three options exist, allowing you to choose from an install kit with no pump, a complete kit that comes with a CP3 pump, or get it as an R900 series performance stroker CP3 pump that provides increased fueling.

As a bonus, the kit makes it simple for you by requiring no tuning. Simply drop it into your truck and you’ll be good to go with your concerns over the CP4 behind you.

If you are debating whether this is truly enough of an issue to warrant your concern, simply keep in mind that the CP4 pump on the Cummins has proven a significant enough problem for the 2021 model year that Cummins themselves have gone back to using the CP3 pump.


Don’t let your truck suffer weak performance, or worse, tens of thousands of dollars in repairs from a known issue that can be avoided. Install the BD Diesel CP3 conversion kit and put the worry – and the CP4 – behind you.

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