One of the most important things to know about the modern 6.7L Cummins is which high-pressure fuel pump it has. Earlier trucks used the proven Bosch CP3, while 2019 and newer trucks switched to the Bosch CP4.2. That difference matters, because a CP4.2 failure can be extraordinarily expensive.
The CP3: proven and durable
From 2007.5 through 2018, the 6.7L Cummins used the Bosch CP3 high-pressure pump. The CP3 has a long track record across many diesel platforms and is regarded as one of the most robust and forgiving high-pressure pumps ever made. It tolerates less-than-perfect fuel better than its successor and rarely fails in a way that destroys the entire fuel system.
The CP4.2: efficient but higher risk
Starting in 2019, the 6.7L moved to the Bosch CP4.2. The CP4.2 is more efficient and helps meet emissions and performance targets, but it has a well-documented reputation for catastrophic failure. When a CP4.2 fails, it can send metal debris throughout the entire fuel system.
- Contamination on failure. A grenaded CP4.2 sends metal shavings downstream into the rail, injectors, and lines.
- Whole-system damage. Because of that contamination, a failure often means replacing the pump, injectors, rail, and lines, which is a very expensive repair.
- Fuel sensitivity. The pump is less tolerant of poor fuel quality and low lubricity, which are thought to contribute to failures.
The CP3 conversion option
Because of the CP4.2's reputation, a popular option for 2019 and newer owners is a CP3 conversion. This swaps the CP4.2 for the older, more durable CP3 along with the necessary supporting components. Owners choose this for peace of mind, especially if they tow heavy, put on high miles, or simply want to avoid the risk of a catastrophic fuel system failure.
- Replaces the CP4.2 with the proven CP3.
- Reduces the risk of a failure that contaminates the whole fuel system.
- Often chosen as preventive insurance rather than after a failure.
A conversion is a significant job with supporting parts involved, so it is worth planning carefully and using quality components.
Protecting either pump
Whether you have a CP3 or a CP4.2, good fuel habits help:
- Use quality fuel and consider a fuel additive for lubricity where appropriate.
- Change fuel filters on schedule with quality filters.
- Consider added filtration and water separation, which is especially valuable protection for the CP4.2.
- Keep the tank reasonably full to limit condensation and water.
Frequently asked questions
Which years have the CP4.2 and which have the CP3?
The 6.7L Cummins used the durable CP3 from 2007.5 through 2018 and switched to the CP4.2 for 2019 and newer trucks. Knowing your year tells you which pump you have.
Why is the CP4.2 considered risky?
When a CP4.2 fails, it can send metal debris throughout the entire fuel system, requiring replacement of the pump, injectors, rail, and lines. That potential for whole-system contamination is why many owners consider it higher risk than the CP3.
Is a CP3 conversion worth it?
Many 2019 and newer owners think so, especially those who tow heavy or put on high miles. It swaps in the more durable CP3 and greatly reduces the risk of a catastrophic fuel system failure. Contact sales@coredieselparts.com to discuss whether it fits your truck and goals.
Need parts or a second opinion on a diagnosis? The team at Core Diesel Parts can help you match the right components to your truck. Email sales@coredieselparts.com with your year, engine, and symptoms and we will point you in the right direction.
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