When Cummins enlarged its famous inline-six to 6.7L in 2007.5, it kept everything owners loved about the engine while adding the displacement and technology to meet modern demands. Since then the 6.7L has evolved steadily, climbing to towing and torque figures that would have seemed impossible in the 5.9L days. Here is how the current Cummins came to be and how it has changed.
From 5.9L to 6.7L
The jump to 6.7L increased displacement for more low-end torque and gave engineers room to meet tightening emissions rules. It retained the inline-six layout, the stout bottom end, and the intake grid heater for cold starts that define the Cummins family. The larger engine offered more grunt right where towing lives, reinforcing the Cummins reputation for effortless pulling power.
Modern emissions hardware
The 6.7L arrived as diesels were adopting comprehensive emissions systems. Over its life it has used EGR, a diesel particulate filter, and, since around 2010 to 2011, selective catalytic reduction with diesel exhaust fluid (DEF). This hardware keeps the engine clean and compliant, and it means owners manage regeneration cycles and DEF refills as routine maintenance. A healthy emissions system is central to trouble-free ownership.
The move to the CP4.2 pump
Earlier 6.7L Cummins engines used the well-regarded Bosch CP3 high-pressure pump. Around 2019, the Ram 6.7L moved to the CP4.2 pump, which is more efficient but more sensitive to fuel quality and lubrication. As on other CP4.2 applications, clean fuel and diligent filtration matter, and some owners add extra fuel system protection for peace of mind. Knowing which pump a truck has shapes how you maintain it.
Climbing power and towing figures
Across successive updates, Cummins and Ram steadily raised the 6.7L's output, with the high-output versions reaching torque numbers that lead the class. Combined with strong transmissions and improved cooling, the modern 6.7L is a formidable tow rig. Yet it still traces its character straight back to the inline-six that transformed the Ram in 1989.
Matching maintenance to your 6.7L's era
Because the 6.7L Cummins has evolved considerably over its long run, the right maintenance approach depends on which version you own. Earlier trucks with the Bosch CP3 pump are known for a durable high-pressure system, while later trucks that moved to the CP4.2 pump around 2019 call for extra attention to fuel quality and filtration, since that pump is more sensitive to contamination. Identifying which pump your truck uses is the first step toward protecting it correctly.
The other constant across the 6.7L's life is the emissions system. Over the years it has carried EGR, a diesel particulate filter, and DEF-based selective catalytic reduction, and keeping all of it healthy is central to trouble-free ownership. Letting regeneration cycles complete, using quality DEF, and addressing warnings promptly keeps the truck out of reduced-power modes. Combine that with clean fuel and regular service, and the modern 6.7L delivers the class-leading torque and towing capability that have kept it at the front of the pack, while still carrying the inline-six character that defines the Cummins name.
Frequently asked questions
When did the 6.7L Cummins replace the 5.9L?
Cummins introduced the 6.7L around 2007.5, enlarging the engine from 5.9L for more torque and to meet tightening emissions standards while keeping the inline-six design.
Which fuel pump does the 6.7L Cummins use?
Earlier 6.7L engines used the Bosch CP3 pump. Around 2019, the Ram 6.7L moved to the CP4.2 pump, which is more sensitive to fuel quality, making clean fuel and good filtration important.
Does the 6.7L Cummins use glow plugs?
No. Like all Cummins diesels, the 6.7L uses an intake grid heater to warm incoming air for cold starts rather than glow plugs.
Restoring or maintaining one of these engines? Email our team at sales@coredieselparts.com with your year, engine, and VIN and we will confirm the correct part before you buy.