How to Reduce After-Treatment Issues
I don’t think that anyone who works on trucks equipped with aftertreatment systems appreciates them. That might not be true. No one financially responsible for a truck equipped with an aftertreatment system appreciates them. Those who do work on them may find the recurring problems annoying but one reality is that the air in diesel shops is a lot more pleasant than it used to be. That said, aftertreatment systems are finicky, to put it gently. The conditions they work in are extreme and government mandates demand that they work well enough to reduce emissions.
While sensors and other components have gotten a lot better, they’re still riddled with problems. Add to that sub-par maintenance and repairs and you have even more problems on your hands. Unfortunately, many problems with the aftertreatment systems are usually self-inflicted by small mistakes or neglect.
Clean fuel and good oil
The whole point of the aftertreatment system is to change what comes out of the engine. So it makes sense that what goes into the engine, and how, have a huge impact on what comes out. Aftertreatment systems are a pretty amazing mix of technologies designed to reduce negative emissions. But it is limited how good of a job it can do in the field and in reaction to very quick changes. By making sure what goes into the engine in the form of fuel, and how well lubricated that engine is with oil you will make big inroads into helping the system perform better for longer.
After all, aftertreatment systems are systems, not just one or two components. There’s the EGR valve and cooler, the DOC, the DPF and the SCR as well as the DEF pump and injector. Just the DEF pump and its lines are complicated enough and dependent on many other things going right including the engine and DOC temperatures.
Clean intake system
The better the air coming in, the better it will be going out. When an engine is pulling air hard through a clogged air filter, it’s not going to perform as well as it can. In extreme cases, a clogged air filter can cause check engines and a noticeable lack of power all on its own. Most people do know this and anyone inclined to read an article about reducing aftertreatment-related issues probably already handles this.
The real issue that begins in the intake system, all the way upstream, is the intake manifold pressure sensor. This sensor is mostly responsible for the engine computer's decisions on how much fuel to send depending on the fuel pedal position. The air-to-fuel ratio is incredibly important to a clean running engine and if an engine doesn’t know how much air is coming into the cylinders it’s liable to send the wrong amount of fuel.
The wrong air-to-fuel ratio will result in a rich or lean mix. It’s typically the rich that we worry about, especially with DPFs. The black smoke that you see coming from a truck's exhaust system is unburned fuel, known as diesel particulates. Diesel particulate is what makes up the D and the P in the Filter known as the DPF. So keeping this sensor clean as well as the air filter will help reduce the demand on the DPF.
Clean sensors
There’s more that you can do than just clean the intake manifold pressure sensor. The downstream sensors also merit a good cleaning. A good quality electronics cleaner in an aerosol can and a soft brush will do the trick. Let the cleaner work and don’t brush too hard.
Another common issue is the DPF pressure differential. Essentially the difference (the Delta) in pressure from the DPF intake and the outlet need to be measured. In some climates more than others, humidity can build in the lines connecting to the sensor in the center. A gentle cleaning of this as well as proper positioning so ay humidity drains out will help.
Go through your particular truck's system from intake to tailpipe and see which sensors you could give a gentle cleaning to not just extend the life but to improve the performance of the sensor as well.
Tidy up wiring
The final important component for the reliability of an aftertreatment system is the wiring. The DPF gets incredibly hot and it’s very rare that any wiring is subjected to a similarly hostile environment. Typically, the OE knows where the hottest points of contact are and will put some sort of protective sleeve or shield. Keep these where they are and replace them if necessary. You’ll probably notice orange-colored high-heat tie wraps. If and when you replace these replace them with the same. Standard tie-wraps are not at all geared for this kind of environment and can fail or melt.
Conclusion
As discouraging as aftertreatment systems can be, you are not hopeless nor are you without any way of fighting back. By putting regular maintenance and these tips into your work you will experience fewer problems than you otherwise would. While we might bemoan the existence of these systems, they’re here whether we like them or not. Just about every fleet has nothing but trucks with aftertreatment systems evening the playing field. If you learn to better maintain and operate your aftertreatment systems than another fleet then this will be a competitive cost-saving advantage.