Keith Browning Posted February 23, 2018 Share Posted February 23, 2018 I am not necessarily over run with these but for the volume of medium duty trucks I see there have been a number of SCR catalyst failures in my shop. These would be on the ISB 6.7L of course. They fail for efficiency with no real detectable reason either. I was wondering if anyone else sees these failing. Quote Link to comment Share on other sites More sharing options...
JoeR Posted February 23, 2018 Share Posted February 23, 2018 Every Cummins with a DEF Fluid Quality Code has been DEF deposited at the injector. I see one a week. Look at the NOx Adaptation PIDS. If either Inlet or Outlet Adaptation is over 100 ppm, yank the injector and look in the hole. This is what you'll find. (See Pic) Clean the decomposition tube with hot water if necessary, and clean the DEF injector with a wet rag. Run the SCR Performance or SCR System Tests to get it out of derate. 1 Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted February 23, 2018 Author Share Posted February 23, 2018 The hole on this recent one was clean when I removed the injector to run the dosing measurement test. I ran the SCR test twice and it failed both times. Good tip though! Quote Link to comment Share on other sites More sharing options...
JoeR Posted February 23, 2018 Share Posted February 23, 2018 I'd still be curious to see what the NOx in/out and NOx adaptations were reading going down the road. If the DEF is good, NOx sensors are correct, and SCR Temps aren't hotter on the outlet, you're probably looking at a bad SCR. I've heard of Cummins replacing them, but haven't ever seen a bad one myself. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted February 23, 2018 Author Share Posted February 23, 2018 INSITE has an automated SCR test that does a warm up, deposit burn, tests the NOx sensors then tests the SCR efficiency. I ran it twice and it failed both times. The dosing test put out 100 ml with a nice spray and the DEF was 32.5%. I trust the test and the truck is fixed every time. Wish ford had this automated test. Quote Link to comment Share on other sites More sharing options...
Buddy_M Posted February 24, 2018 Share Posted February 24, 2018 I've had a run of SCR failures with the Ram diesel applications also. Most of them have been covered under a recall. I wonder how similar the SCR design is between the light duty Ram pickups to the medium duty use or if they may even be the same since that part is typically supplied by Cummins I belie e. Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted February 24, 2018 Author Share Posted February 24, 2018 I work on Rams occasionally as well and the system as a whole is the same as the Ford medium duty application but the DOC, DPF and SCR are smaller on the Ram trucks. Also on the Ford medium duty there are 6 or 7 different configurations. Now I have done a couple Ram recalls and that was to eliminate the intermediate NOx sensor... well Cummins has no recall on them but when I have to replace one I need to convert them from a 3 sensor to a two sensor system if I have to replace the SCR - Cummins TSB 150105 which also requires changing a wire harness and the base engine calibration. Quote Link to comment Share on other sites More sharing options...
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