$12,000 failure

[Guest 04Mach1]

Just thought I'd share why I'm scared of the DEF and NOx nightmare that EPA10 and newer diesel engines are plagued with. This isn't the first SCR failure I've seen and I'm sure it won't be the last.

 

Anyway truck came in severely derated doing the "5 mph crawl of shame". DDDL8 revealed active SPN 3364 FMI 0 and SPN 3364 FMI 17 faults which equate to the ACM saying the truck has "poor DEF quality" due to low NOx conversion efficiency.

 

A check of DEF concentration with a refractometer showed 32.5% which is exactly what is needed. I then checked DEF dosing quantity which again was perfect at 4.5 ounces using the specific DDDL8 test. I then did a parked Regen which will show NOx conversion at operating high SCR temperature. This showed only 20%-30% NOx conversion efficiency at with the SCR temperature of around 1000*F and a very audible rattle with in the 1-box could be heard. NOx conversion efficiency during Regen should not be below 70% during Regen and most of the time is above 90% with a healthy SCR. During normal operation NOx conversion efficiency should be 85% or better to keep from causing NOx or DEF related faults the will cause engine derating.

 

Anyway due to the audible rattle with in the 1-box and the very low NOx conversion efficiency of the SCR the 1-box got replaced at a substantial expense of $12,000 and some change.

 

 

 

[Mopar1973Man]

 

SCR, DEF, EGR and all the alphabet smog junk is a joke. 

[notlimah]

Wow, makes it tough to see the justification for these systems when repairing them is so costly.

 

What do you think caused the failure?

[IBMobile]

3 hours ago, notlimah said:

Wow, makes it tough to see the justification for these systems when repairing them is so costly.

The justification is clean, take a deep breath, air and higher, now empty your wallet, transportation costs.  

[Dieselfuture]

Something to consider when buying a new diesel vehicle, all these hidden costs that are associated with longetivity.

[Guest 04Mach1]

On 12/9/2018 at 4:48 PM, notlimah said:

Wow, makes it tough to see the justification for these systems when repairing them is so costly.

 

What do you think caused the failure?

Yeah they are very costly to repair. IMO most of the DPF and SCR failures can be avoided by NOT idling the engine. When idling cylinder temps are low causing incomplete combustion which in turn leads to excessive soot that the cold ATD can not turn into ash which leads to DPF plugging. Now you perform a Regen and all the sudden you have all the soot plugging the DPF start burning and turns into an uncontrollable inferno in the ATD itself that will either crack or melt the DPF and SCR ceramic material. About 1400*F is the maximum safe operating temperature for an ATD, I've seen a few light off when the 7th injector started injecting fuel at about 700*F and within seconds the ATD is above 2000*F to where the DPF and SCR is ruined very quickly. In the case of the last 1-box I replaced I feel excessive idling led to the SCR failure. There was an inactive SCR inlet temperature high fault stored in the ACM from 2 days prior to the DEF quality faults becoming active. Unfortunately with Detroit 1-box's if either the SCR or DOC fail the 1-box has to be replaced since they are not replaceable, however the DPF is replaceable. With Cummins or any manufacturer other than Detroit the DOC, DPF, and SCR can be replaced independent of each other.

 

Here's a quick animation of the flow of a Detroit Diesel 1-box.

 

 

[Mopar1973Man]

 

[CUMMINSDIESELPWR]

in colorado my truck ran cleaner than most cars stock per the emission reading