CCM Posted May 2, 2017 Share Posted May 2, 2017 Hello all, I'm working on a 2012 Mack MRU613 (Refuse) The unit was brought in with check engine/regen issue. Codes showed high soot level. Pulled filter and found it to be pushed out of housing. List of items we checked and replaced. Inspected diff ports, Turbo, Boost leaks, Adjusted valves and Injectors. Replaced dpf, Diff pressure sensor to updated version. All seemed to be good. Ran regen and had no codes. Unit returned just a few days later with high soot level issue. Went back through and rechecked everything again including the things we forgot to the first time including the egr valve. We have no flow with the egr valve electrical unplugged. Updated the acm and eecu software. With the exhaust pipe removed from the dpf we can load up the engine and it will blow black smoke. Possible injector issue? Any other ideas? Quote Link to comment Share on other sites More sharing options...
BGarofalo Posted May 3, 2017 Share Posted May 3, 2017 An injector certainly could be a cause. I would look toward the VGT turbo first. Stuck or sticking vanes can cause smoke and quickly plug up a dpf. I run into a lot of regen problems stemming from the turbo. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted May 3, 2017 Share Posted May 3, 2017 Is it a spark assisted ( has spark plugs in the bottom) DPF? I cant remember the year they got rid of the EMCON spark assisted DPF and went with the standard model like the CHU/CXU. If it is, the real question , can it do a rolling regen? Quote Link to comment Share on other sites More sharing options...
CCM Posted May 3, 2017 Author Share Posted May 3, 2017 @BGarofalo, Injectors is our thought but how do you explain a hunch to the customer. Hero if it fixes it and zero if it doesn't. We removed the vgt actuator and performed a manual lever test and it moved fine. We also unplugged the egr valve and performed a stall test and it still smokes. Did a cylinder cut out test and all injectors seem to be hitting evenly. @Mackpro, It is the spark assisted system. I think it does a regen but its putting out so much black smoke (soot) that it cant keep up. Thanks for the replies Quote Link to comment Share on other sites More sharing options...
Mackpro Posted May 3, 2017 Share Posted May 3, 2017 A cracked injector tip is way more common in the MP-7 than the MP-8. However a cracked tip usually shows as hard starting or no starting. Id pressurize the whole intake system and make sure the metal "U" pipe at the back of the EGR cooler is not leaking. Quote Link to comment Share on other sites More sharing options...
CCM Posted May 3, 2017 Author Share Posted May 3, 2017 That's good info to know on the Injector tip issue. I wasn't aware of that. Unit has no issues on starting. We checked to intake system and repaired the leaks we found. I do have one issue that we are unsure about. When we had to pressure test equipment hooked up the the inlet of the turbo we have air leaking from outlet of turbo. Normal or not? Quote Link to comment Share on other sites More sharing options...
Mackpro Posted May 3, 2017 Share Posted May 3, 2017 Yes , thats normal, the EGR Valve is not air tight , even when new. The air comes back around into the exhaust manifold. I wonder if the truck has an engine brake? The brake pistons could be backing out but you should have noticed it while adjusting the valves. Engine Brake piston.pdf Quote Link to comment Share on other sites More sharing options...
CCM Posted May 4, 2017 Author Share Posted May 4, 2017 It does have engine brake. And that was my thought also but we didn't notice any issues while adjusting the valves. Love getting the ones that drive you crazy. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted May 4, 2017 Share Posted May 4, 2017 You do a "cylinder balance test" in Tech Tool. Sometimes it shows a bad cylinder thats hard to find. Quote Link to comment Share on other sites More sharing options...
CCM Posted May 4, 2017 Author Share Posted May 4, 2017 @Mackpro, I performed that test but it never makes any sense to me. Here are the number after running the test for 10 mins #1cyl (4) #2cyl (9) #3cyl (-10) #4cyl (9) #5cyl (-8) #6cyl (-3) We also did a cyl compression test with PTT and it first showed bad cyl #4. Ran test again and it showed #2 & #4. Tested again and it showed all good. Thanks again for responding with the suggestions. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted May 5, 2017 Share Posted May 5, 2017 You got something going on for sure. Let me do some digging in the morning. Did you ever have any injector fault codes for this truck? If so , what were the FMI's? Quote Link to comment Share on other sites More sharing options...
turckster Posted May 5, 2017 Share Posted May 5, 2017 Did you use Tech Tool to verify the egr was not flowing or did you remove a egr pipe and verify no flow? We/I use a zip tie to attach a nitrile disposable glove to the egr side of a pipe, start the engine (egr valve unplugged). If the glove expands and pops the egr valve is bad. You should be able to hold your hand over the pipe with little resistance if the valve is good. We see this a lot with trucks that require frequent regens. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted May 5, 2017 Share Posted May 5, 2017 Turckster is right . Your EGR valve should only have 2 lines going to it. One from the back and one up from the bottom. If it has a extra line on the bottom ( steel braided drain tube) then I would change it, The ones with the drain tube gave us lots of issuses. EGR valve no drain tube.pdf Quote Link to comment Share on other sites More sharing options...
CCM Posted May 5, 2017 Author Share Posted May 5, 2017 @Mackpro, Thanks for doing the research. there were no Injector codes or any fuel related codes. That's what has us puzzled. The egr valve does have the updated one on it already (no drain) @Turckster, We did checked for any flow but we haven't tried the glove trick. We will try that this morning and see what we come up with. Quote Link to comment Share on other sites More sharing options...
CCM Posted May 5, 2017 Author Share Posted May 5, 2017 So, we performed the glove test on the egr and it did inflate the glove. replaced the egr valve and re-tested. It still put air into the glove but not nearly as fast. Still getting a lot of black smoke. I's it possible the intake manifold and intake ports are just filled with excessive soot and is going to take time to clear out? Quote Link to comment Share on other sites More sharing options...
JSmackchu613 Posted February 8, 2023 Share Posted February 8, 2023 Hello did ever fix it. My mack has a new turbo it also blow black smoke between gears. Quote Link to comment Share on other sites More sharing options...
fjh Posted February 8, 2023 Share Posted February 8, 2023 Bro post your year and model in a new thread we may be able to sort you out! Quote Link to comment Share on other sites More sharing options...
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