• 2019

Get Your Engine Running

Keeping Diesel Engines Running at Peak Efficiency

Performing regularly scheduled maintenance is crucial to ensuring the long service life for any engine. This is especially true for diesel engines. Diesel engines are becoming more popular in the United States, so it’s a good idea to become accustomed to the specific maintenance schedules for these powerplants.

FCA US LLC offers several diesel engines throughout its lineup. The size of these engines cover a wide range of displacement. From the 2.0L I4 turbo diesel used in the Jeep® Renegade, Jeep Liberty, Jeep Cherokee and Dodge Journey, to the 2.8L turbo diesel, which is an option in the Chrysler Grand Voyager, Jeep Wrangler and Chrysler Town & Country. Diesel engines are well represented in most FCA US lineups. There are also a pair of 3.0L diesels. One is a V6 turbo diesel installed in the Jeep Grand Cherokee, Chrysler 300, Ram 1500 and Ram ProMaster®. The other is the popular 4-cylinder diesel that has been used in the Ram ProMaster since 2014.

Finally, at the top of the heap is the big 6.7L Cummins turbo diesel that is the workhorse in the Ram heavyduty lineup, starting with the 2500 and up through the 4500/5500 cab chassis. Variations of this engine have been used in Dodge pickup trucks for 15 years. It’s easily the most popular diesel engine in the FCA US lineup. The maintenance discussion on this particular diesel engine follows.


As with gasoline engines, regular oil changes in diesel engines are also critical to long engine life. There are two major differences, however, where oil is concerned. The first is capacity. While a  typical gas engine will have an oil capacity of about 5 quarts, the big Cummins requires 12 quarts.

The second, and more important difference, is the oil type. The diesel engine uses high-quality, low-ash, multi-viscosity oil. Plus, when the oil filter is replaced, the new one has to be filled with clean oil. The interval for oil changes with a diesel is 15,000 miles, or 500 hours, whichever comes first.

While the oil filter should be changed every time the oil is changed, the air filter and fuel filters should also be changed every 15,000 miles. Make note, there are two fuel filters on the Cummins engine. Fuel filter 1 is located on the engine. Fuel filter 2 is located on the frame near the fuel tank. The fuel filters protect the fuel injection pump and fuel injectors by removing contaminants from the fuel.


Selective Catalytic Reduction (SCR) is a technology that uses a urea-based diesel exhaust fluid (DEF) and a catalytic converter to significantly reduce nitrous oxide (NOx) emissions. The system accomplishes this by injecting small quantities of DEF into the exhaust system upstream of the catalyst, where it vaporizes and decomposes to form ammonia and carbon dioxide. The ammonia is the desired product which (in conjunction with the SCR Catalyst) converts the NOx to harmless nitrogen and water. While a diesel exhaust fluid (DEF) level gauge displays the actual level of DEF in the DEF tank, the level of the DEF should be checked every 7,500 miles. Refill the tank, if necessary. The DEF filler cap is inside the fuel fill door (see Figure 1).

Note: Diesel exhaust fluid (DEF) contains urea; do not get this substance in your eyes; do not swallow it; in case of contact or ingestion, contact a physician immediately.

Figure 1


Exhaust gas recirculation is an emissions technology used in both gasoline and diesel engines. The system is designed to reduce oxides of nitrogen (NOx) in the exhaust system by reducing combustion temperatures. This is done by introducing inert gas exhaust) into the combustion process. The intake air charge is diluted by a precisely metered amount of exhaust gas for the operating mode.

In a diesel engine, such as the Cummins 6.7L design, a buildup of soot can occur. It’s not something encountered in a gasoline engine. Since soot is present in the exhaust stream, it will be present in the EGR valve assembly, as exhaust gas is used to cool combustion temperatures. The EGR valve in this particular diesel engine has two soot guards. As a result, the EGR valve requires periodic cleaning. While this task is not listed on maintenance charts, experience has found that it should be cleaned every 60,000-70,000 miles.

Let’s review the procedure for cleaning the EGR valve. See Figure 2 (an exploded view of the assembly). First, remove the EGR valve assembly from the engine, then remove the four screws (7) that attached the valve housing (1) to the valve motor (6). Remove the motor and its shim (5) from the housing.

Note: When the EGR valve is re-assembled, the EGR valve motor and shim must be reinstalled onto the EGR valve housing.

Figure 2

Using two fingers, press down on the valve spring retainer (3) to unlock the valve keepers (4). Remove the valve spring retainer and the valve spring (2). Lightly press on the valve stem (not shown) about 3/8” to force the valve faces from the valve seats. Using a small, steel wire brush, clean away any loose soot from the EGR valve housing.

Refer to Figure 3. The EGR valve is comprised of two poppets (2), two seats (3) and a lower soot guard (4). An upper soot guard (5) is pressed into the housing. Using the same steel brush from the previous cleaning step, clean the soot from both poppets and seats. After cleaning, be sure that there is metal-to-metal contact between both poppet/seat interfaces. This will allow the valve to fully close.

Figure 3

Bend the steel brush to a 45° or 90° angle and while rotating the shaft, clean the soot between the lower soot guard (4) and the upper soot guard (5) interface. Next, submerge the entire valve housing in a solution of hot water and Mopar® EGR System Cleaner (ESC). This solution should be one part ESC and four parts water. Soak the valve for one hour, occasionally pushing the shaft through its full stroke.

Remove the valve assembly from the cleaning solution. Completely remove the remaining soot from the entire valve assembly. Rinse the EGR valve housing in hot water until all cleaning solution is rinsed clean. Using shop air, blow-dry the EGR valve completely. Assemble the valve spring and the retainer to the housing.

As you can see, two of the most important maintenance tasks (DEF level and EGR valve cleaning) ensure that the emissions level from this engine remain in compliance.

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