Cummins Turbodiesel FAQ

Frequently Asked Questions about the 5.9L & 6.7L Cummins

When was the Cummins Engine Co. founded?

Clessie L. Cummins founded the Cummins Engine Co. (now Cummins Inc.) in 1919, building small diesel engines. These early engines were by-and-large defective, and it was not until 1930 that the company produced its first commercially successful diesel engine. The reputation of the Cummins brand has since grown to become synonymous with reliability and longevity.

What other applications are Cummins engines used in?

Cummins designs and manufactures engines for a wide variety of industrial, agricultural, and on-highway applications. Dodge/Ram trucks actually account for a very small amount of the company's business. In terms of on-highway applications, Cummins engines can be found in many medium and heavy duty applications (class 4 - 8). The engines range in size and configuration, from small 4 cylinders to massive, 3600 cubic inch V-16 diesels for marine applications. Name an industry in the United States that relies on diesel engines and Cummins is likely to be at the forefront of innovation in the segment.

When did Dodge start offering the Cummins in its pickups?

1989 was the first model year that Dodge offered a Cummins engine. The original 6BT (5.9) was rated at 160 hp and 400 lb-ft of torque. At this time, Cummins' closest competitor in the market was International/Navistar, whose 7.3L IDI produced 185 hp and 360 lb-ft of torque in Ford 3/4 and 1 ton pickups. Detroit's 6.2L, used in GMC and Chevrolet pickups, trailed by a large margin with 130 hp and 240 lb-ft of torque for the 1989 model year. The Big 3 have since been competing profusely for market share.

What does "6BT" stand for?

The acronym "6BT", which denotes the 5.9L 12v Cummins (1989 - 1998 model years), stands for 6 cylinder, "B series", turbocharged. The Cummins "B series" is a family of inline cylinder diesel engines including 4 and 6 cylinder models.

What does "ISB" stand for?

The acronym "ISB" is short for "Interact System B", where "Interact System" denotes that the engine is controlled electronically (opposed to mechanically), and the B refers to the fact that the engine is a Cummins "B series" design. "Cummins ISB" is typically used in reference to the 5.9L 24 valve Cummins, successor of the mechanical 6BT (12 valve). It was available from 1998 to 2007 model years, then replaced by the 6.7L ISB.

What does "Gen 1", "Gen 2", "Gen 3" refer to?

"Gen" refers to the generation of Cummins engine in regards to Ram pickups. The following chart might help better understand how Cummins describes the various generations:


Model Years


Generation 1

1989 - 1993

1st Gen, 5.9L 12v Cummins, VE44 rotary style injection pump

Generation 2

1994 - 2002

2nd Gen, 5.9L 12v Cummins 1994 - 1998, P1700 injection pump. 5.9L 24v Cummins 1998.5 - 2002, electronically controlled VP44 injection pump.

Generation 3

2003 - 2009

3rd Gen, 5.9L 24v Cummins, common rail injection, 2003 - 2007. 6.7L Cummins, 2007.5 - 2009.

Generation 4

2010 - current

4th Gen, 6.7L Cummins


Does Ford own Cummins?

This is a rumor, plain and simple - Ford does not, and has never owned Cummins. This rumor likely spawned from the fact that Ford was, at one period of time, a Cummins shareholder. Even then, Ford did not own enough of Cummins' stock to participate in or influence the company's decisions. Ford has historically engaged in business dealings with Cummins, as Cummins' engines have been offered in Ford's medium duty vehicle lineup off-and-on throughout the years.

What are the advantages of an inline 6 diesel?

This question is most often asked with the intention of supporting the claim that an inline 6 cylinder engine produces more torque, and at lower engine speeds than a traditional V engine. Alas, it would be fallacy to make such an assumption, as manufacturers of V diesels have proven that a V diesel can be engineered to match or even surpass the output of an inline engine, cubic inch for cubic inch. V diesels also produce flat, board torque curves that peak at relatively low engine speeds. This is not to say that inline engines are not superior in many categories.

The spacial limitations of an inline 6 cylinder actually encourages an under-square bore-to-stroke design. That is, the engine utilizes a relatively long stroke with a comparatively small bore. A long stroke design promotes torque production at low engine speeds, as the stroke length dictates the degree of mechanical advantage in converting the heat energy of burning fuel into usable mechanical energy. A longer stroke requires a longer crankshaft journal offset. The length of the crankshaft journal offset from the crankshaft center can be conceptualized as a lever arm - consider a breaker bar, the longer the bar, the more mechanical advantage the user experiences when a force is applied to the handle. In this sense, the inline 6 engine design is favorable from a design perspective. This is not to say the same can not be accomplished in other engine configurations, but a completely different set of obstacles will arise in the design process.

Inline 6 engines are inherently balanced (but this does not apply to all inline engines). The result is smooth operation, minimal vibration, and steady harmonic transitions between light and heavy engine loading (particularly at low engine speeds). The fact that the straight 6 engine is naturally balanced allows for scalability, which is one of the reasons why you'll see such similarity between large and small engines of the same engine family.

Inline 6 cylinder engines are narrower than a V engine, which allows for locating components on the sides of the engine. The turbocharger on the Cummins diesel, for example, is easily accessible from the passenger side of the engine block, as opposed to many V engines which locate the turbocharger on top of or near the rear of the engine. This can reduce maintenance and repair cost, as well as vehicle downtime. This is particularly important in larger trucks and commercial applications, as even major repairs can be performed without removing the engine from the chassis. Finally, an inline engine is mechanically simpler than a V engine as it only has a single cylinder head.

What is a "common rail" Cummins?

A common rail (CR), more specifically a high pressure common rail, is an injection type that uses a shared delivery tube to provide fuel to each individual injector. The rail is pressured via a high pressure injection pump, and each injector is individually fired electronically. This is in contrast to a mechanical system, which uses an injection pump to feed high pressure fuel to each injector through individual lines (a 6 cylinder engine would therefore have 7 fuel lines - one low pressure inlet and one high pressure outlet for each injector). The common rail is a far superior design, and is the injection type of choice for all modern diesels.

What is a diesel particulate filter (DPF)?

A diesel particulate filter, or DPF, is an emissions control device that captures exhaust soot produced by the engine. The filter is cleaned through a process called regeneration, of which there are two modes. Passive regeneration occurs during normal driving whenever conditions are right to "burn" the particulates in the filter. This typically occurs during long periods of highway driving. Active regeneration occurs once a predetermined filter capacity has been reached, which indicates that conditions have not been met to inhibit passive regeneration. At this point, the engine will intentionally release fuel into the exhaust stream, allowing temperatures to be reached such that particulate matter in the filter will be burned off. The DPF was introduced with the 6.7L Cummins for the 2007.5 model year.

What is diesel exhaust fluid (DEF)?

Diesel exhaust fluid is required for selective catalytic reduction (SCR) systems, which were first required for 2011 model chassis cabs and 2013 model consumer pickups with the 6.7L Cummins. DEF primarily contains a concentration of distiled water and urea, the active ingredient. It is injected into the SCR catalyst (the quantity of which varies with load) where the reduction reaction takes place, converting harmful nitrous oxides (NOx) to safe nitrogen gas and water vapor. DEF is stored in a tank, the level of which needs to be maintained at all times.

Does my Cummins have glow plugs?

If someone asks where the glow plugs are on your Cummins are, they are playing a joke on you. The Cummins uses a single heater grid located in the intake of the engine in place of a traditional glow plug system, which requires an individual plug for each cylinder. The purpose of the heater grid is exactly the same as that of glow plugs - to warm the incoming air charge during cold starts. So no, your Cummins does not have glow plugs.