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Showing results for tags 'scr failure'.
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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.
