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The Cummins diesel engine is one of the most popular and successful diesel engines ever made. Clessie Lyle Cummins initially invented the engine for agricultural use, but he also envisioned it being used in passenger vehicles.
Cummins eventually put one of his engines into a 1926 Packard Touring Sedan and drove 300 miles on 30 gallons of fuel, which was an incredible display of fuel efficiency for the time period.
Cummins eventually started his own company and that company would go on to unite with Dodge in the late 1980s. At the time, Dodge was the only major automaker that didn’t have a diesel engine in its passenger trucks. Dodge began building a newly designed truck to go with the Cummins diesel engine and thus the Ram line of trucks was born.
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The first Dodge pickups to hit the market with a Cummins engine had the 5.9-liter, 12-valve version that made 160 horsepower. These trucks were fairly light and not overly complicated, but they got great fuel economy for the time at 20-26 MPG. Enthusiasts still consider this early engine to be one of the most reliable diesel engines ever for a pickup truck.
The 1st generation 5.9-liter Cummins featured some unique specs that weren’t available on other diesel engines of the time, including direct fuel injection and a Holset fixed geometry turbocharger. This allowed the 1989 to 1993 Dodge Ram trucks to make a best-in-class 400-pound-feet of torque. That might not seem like a lot by today’s standards, but at the time it was very impressive.
Was the 1st Gen 5.9-liter Cummins reliable? Considering that there are many of these engines still on the road thirty years later, it seems fair to say that they were quite reliable. They were designed to be durable and long-lasting, and they did not have any complex electronic features or modern emissions devices.
By using an inline-six design, Cummins created an engine that was easy to work on and takes up less space than a V8. For modern diesel enthusiasts, the 5.9-liter has also proved to be easy to modify for power upgrades without needing a lot of additional support parts.
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An upgraded body style was the main feature of the next generation of Dodge diesel trucks. The 5.9-liter Cummins was also upgraded into the second generation with some adjustments. There are two different versions of the 2nd Gen Cummins. The first is a 12-valve engine featured in 1994 through 1998 Dodge trucks, and it is very similar to the 1st Gen engine.
The second version is a 24-valve engine and is featured in the 1998.5 through 2002 Dodge trucks. The horsepower and torque numbers for the 2nd Gen depend on the equipped transmission.
The NV4500 five-speed manual transmission gave the 1994 Cummins 175 horsepower and 420 pound-feet of torque. However, the 1994 Cummins with the 47RH automatic only put out 160 horsepower and 400 pound-feet of torque.
A new turbocharger was also added to the 2nd Gen Cummins engine along with a larger intercooler. This was the upgraded Holset HX35, which was better at sustaining stock boost levels and could hold pressures up to 40 psi.
This later version of the 12-valve Dodge Cummins is still favored by enthusiasts today for racing and other high-performance applications. It’s also well-known for being reliable over hundreds of thousands of miles.
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The 3rd Gen Cummins diesel was in Dodge trucks between 2003 and 2009. This generation of Dodge trucks is one of the most popular because you can get the super reliable 24-valve Cummins engine paired with more modern technology in the cabin and a larger truck overall.
Later in the generation, the 6.7-liter Cummins engine debuted, and it was all-new and very different from the previous engine. The main difference between the 3rd Gen Cummins 5.9-liter 24-valve engine and the 2nd Gen was extra horsepower and torque.
These engines made about 60 more horsepower and 50 more pound-feet of torque. The 3rd Gen 5.9-liter engines were also quieter than the previous generation.
Another major milestone for the Cummins engine was hit during this generation, and that was the introduction of high-pressure common rail fuel injection. This system made the engine more efficient and cleaner than the previous generation. It also allowed the trucks to continue being EGR-free for a few more years.
The 6.7-liter Cummins was introduced midway through 2007 and it was the first Cummins engine to feature EGR and a diesel particulate filter system. These additions helped control emissions, but they also created problems for the engine’s overall reliability.
The first three generations of the Cummins diesel engine are considered the most legendary generations by enthusiasts simply because these engines were extremely reliable, easy to modify for extra power, and did not have complex emission technology slowing them down.
Stay tuned for part two where we look at the two most modern generations of the Cummins engine up to the current generation.
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