springerj10 Posted March 3, 2022 Share Posted March 3, 2022 Got a 2018 Mack MRU with an MP7. Truck has had regen issues since we got it new, been to the dealership multiple times but Mack says they can’t duplicate the issues. Active codes as of right now. P103C00 P20EE00 P046C64 P24F700 Truck is in derate requesting a Sulfur regen. During the regen the Nox inlet is at 1026 PPM and outlet is 1773 PPM. It’s had the SCR box, DPF, DOC, DEF filter, DEF doser, DEF level sensor replaced. Any suggestions on where to go next? Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/ Share on other sites More sharing options...
fjh Posted March 3, 2022 Share Posted March 3, 2022 (edited) Yup start at the other end! make sure you got proper temp ! Turbo spooling properly on regen ? Check turbo Effort possibly sticking ! fuel pressure OK? fuel dowser clean?Dpf sensor ports clear tubes clear? with this junk you need to work front to back ALMOST always! Just sayin Edited March 3, 2022 by fjh 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490801 Share on other sites More sharing options...
springerj10 Posted March 3, 2022 Author Share Posted March 3, 2022 5 minutes ago, fjh said: Yup start at the other end! make sure you got proper temp ! Turbo spooling properly on regen ? Check turbo Effort possibly sticking ! fuel pressure OK? fuel dowser clean?Dpf sensor ports clear tubes clear? with this junk you need to work front to back ALMOST always! Just sayin Turbo bearings went out about a year ago, had a new turbo and actuator installed. Fuel pressure is good. 7th injector is clean, gets replaced annually. DPF sensor ports and sensor are clean. EGR pressure sensor and ports are clean as well. Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490802 Share on other sites More sharing options...
fjh Posted March 3, 2022 Share Posted March 3, 2022 (make sure you got proper temp ) what temps are you seeing? Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490803 Share on other sites More sharing options...
springerj10 Posted March 3, 2022 Author Share Posted March 3, 2022 20 minutes ago, fjh said: (make sure you got proper temp ) what temps are you seeing? Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490807 Share on other sites More sharing options...
fjh Posted March 4, 2022 Share Posted March 4, 2022 (edited) hmmm from what I have seen these are reasonable Look not bad ! duno what to tell ya! Was there any evidence of crystal buildup when they had the box off!?Thinking about a crack in the ash can! quite a common thing Also the nox sensors were chronic on these at one point they had a point where we had been changing them left right and center! You could throw sensors at it looks like they have thrown everything else at it! they could be out of parameter and I believe you must do a learned data reset! Edited March 4, 2022 by fjh 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490831 Share on other sites More sharing options...
Onyx610 Posted March 4, 2022 Share Posted March 4, 2022 I’m really surprised you didn’t put nox sensors on it. Not gonna say that’s the answer, but at this point why not? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490837 Share on other sites More sharing options...
Vmac3 Posted March 4, 2022 Share Posted March 4, 2022 Nox level is higher on the outlet than the inlet. Try an outlet Nox sensor and perform the regen. Make sure you reset learned data as mentioned. It is true that these sensors were and still are failing. V 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490838 Share on other sites More sharing options...
Onyx610 Posted March 4, 2022 Share Posted March 4, 2022 Don’t they read ppm when they arnt up to temp? I forget… Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490839 Share on other sites More sharing options...
Vmac3 Posted March 4, 2022 Share Posted March 4, 2022 No they dont read anything until they are around 5oo degf. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490840 Share on other sites More sharing options...
Joey Mack Posted March 4, 2022 Share Posted March 4, 2022 if I may..? shouldnt T-1 be around 850 degrees? Its been years since I did a forced re-gen with PTT.. jojo Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490846 Share on other sites More sharing options...
Onyx610 Posted March 4, 2022 Share Posted March 4, 2022 Is this a NOx issue and not a regen issue? V had a good observation of NOx output being higher. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490847 Share on other sites More sharing options...
springerj10 Posted March 4, 2022 Author Share Posted March 4, 2022 It is a Nox issue that is throwing fault codes and preventing the truck from being able to do a regen by the button and putting it into limp mode every couple weeks. There is no DEF build up. The Nox sensors have been replaced 3 times in the past 2 years with no change on the values. The Nox outlet has always read higher than the inlet. Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490856 Share on other sites More sharing options...
Popular Post fjh Posted March 4, 2022 Popular Post Share Posted March 4, 2022 (edited) Joe Yup! If you can believe what is on the screen there 23 percent duty cycle dose then that 650 seems reasonable! a normal engine idles at 350 so if you add fuel at a low rate after the fact its going to bring the heat up some! And I will add that with all the trouble we have had with these sensors our guys always went there before first before starting at the front and working back! he should note too if he doesn't know already that once nox sensors are changed the lighting bolt will stay on till the computer has time to reevaluate after the learned dat reset! I was about to post the above ! however you added stuff! So do a learned data reset start an E service repair ticket and see if the Mack gurus can assist you bro! no point in beeting a dead horse ! Edited March 4, 2022 by fjh 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490857 Share on other sites More sharing options...
fjh Posted March 4, 2022 Share Posted March 4, 2022 10 minutes ago, springerj10 said: It is a Nox issue that is throwing fault codes and preventing the truck from being able to do a regen by the button and putting it into limp mode every couple weeks. There is no DEF build up. The Nox sensors have been replaced 3 times in the past 2 years with no change on the values. The Nox outlet has always read higher than the inlet. Just note that these sensors can be effected by dampness I believe they had us move the outlet sensor on several trucks further back away from the y pipe water coming down the stack! Just sayin! Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490858 Share on other sites More sharing options...
Onyx610 Posted March 4, 2022 Share Posted March 4, 2022 This may be a stretch, but did you ever take notice to egr diff pressure during regen? Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490859 Share on other sites More sharing options...
springerj10 Posted March 4, 2022 Author Share Posted March 4, 2022 1 hour ago, Onyx610 said: This may be a stretch, but did you ever take notice to egr diff pressure during regen? I don’t remember what it was at this time, I’ll check after the truck comes back in. Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490861 Share on other sites More sharing options...
fjh Posted March 4, 2022 Share Posted March 4, 2022 22 minutes ago, springerj10 said: I don’t remember what it was at this time, I’ll check after the truck comes back in. Bro if you look at the soot value there If you can believe the screen shot it looks to be working fine! just sayin!😐 These dam aftertreatment systems are a crap shoot to trouble shoot no real cut and dried tests bunch of parts changing BS! 2 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490862 Share on other sites More sharing options...
Onyx610 Posted March 4, 2022 Share Posted March 4, 2022 55 minutes ago, fjh said: Bro if you look at the soot value there If you can believe the screen shot it looks to be working fine! just sayin!😐 These dam aftertreatment systems are a crap shoot to trouble shoot no real cut and dried tests bunch of parts changing BS! That’s what I was thinking about the soot level…is it possible it needs some kind of update? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490866 Share on other sites More sharing options...
fjh Posted March 4, 2022 Share Posted March 4, 2022 ahh maybe Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490867 Share on other sites More sharing options...
springerj10 Posted March 4, 2022 Author Share Posted March 4, 2022 It has the latest software updates. Quote Link to comment https://www.bigmacktrucks.com/topic/69319-2018-mru-mp7-nox/#findComment-490889 Share on other sites More sharing options...
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