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2009 MACK GU813 Excessive Black smoke/ plugged DPF in 3 days


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I have a 2009 MACK GU813 (US07)MP7. truck goes through injectors about every year or 2. This time, the truck had no power and running rough, same as in the past when it needed injectors. we put injectors and cups in it. reset the engine learned data. it ran 1 day and had a regen problem. Blowing black smoke out the exhaust. took the DPF and DOC off and sent them in for cleaning. DPF was cracked. installed new DPF and cleaned DOC. truck ran 3 rays needing a regen everyday. now blowing black smoke out again, but only when i put it in regen. DPF and DOC have a ton of soot on them. assuming the DPF is cracked again. several other techs in our company think its an over fueling problem. But if that were the case, wouldn't the fuel be heating up the DOC and burning everything off? like regening all the time. We can't figure out where all the soot is coming from. Injectors are the right part numbers. Truck runs great and has lots of power when not doing a regen. put it into regen and it almost seems like it is missing or running rougher than normal. with the DPF off we start it and see some black smoke out the exhaust, but not a ton. I did a cylinder balance test and it look pretty even across the 6 cylinders. there was 1 code for injector #6 mechanical system not responding after i put the new ones in. cleared it and it hasn't come back after a few days. My boss wants us to pull injectors out to see if we see anything wrong. I've seen posts about black smoke and people have said turbo or EGR.  Any help would be appreciated. we are lost.

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Posted (edited)

Assuming this is a trash truck with your name, I could see regens being quite frequent. It might not be that the engine is the issue but maybe the after treatment system is and not properly doing a regen and face plugging your filters. Also are you sure the driver isn’t just ignoring the regen light and keeps driving?

Edited by Onyx610
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Yes, it is a Roll-off truck. the first couple regens had normal temps(1100 or so) and completed in about 25 minutes. the last regen it was blowing out so much black smoke right away, I cancelled it. i just don't see a new filter needing to regen every day. should go awhile (days) before needing a regen, right? We had thought of the driver being the issue because the switch has the regen button that you can disable it. but another driver was in it yesterday and he wouldn't even know to disable it. each day it was only in stage one. i did find it odd that it said only like 130% and the thing was completely plugged. maybe the differential pressure sensor not working. not telling the truck to regen when it needs to? there are no codes for it but maybe it failed in range? We just have to figure it out or i will be cremated for wrecking another $1500 DPF. Thanks for the reply

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what are the things that create a lot of soot? soot is unburnt or incompletely burnt fuel correct? it just seems to me like there is more soot in there than there should be.  it seems like this didn't happen until i put new injectors in it. But how do i prove that it is the new injectors over fueling. they would have to be bench tested . the truck does have 549, 082 miles and 25,015 hrs. on it. i wish i could just have the dealer look at it but the boss wouldn't like that idea. ($$$)

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Posted (edited)

1st pic is DOC now. 2nd and 3rd are the DPF we replaced 1st time. (was new in Dec. of 2021) pic 4&5 are the DPF just put in a last week.(my co-worker blew it out. it did look worse)

412724DOC.jpg

412724DPF1.jpg

412724DPF2.jpg

412724DPF3.jpg

412724DPF4.jpg

Edited by Wasteman1
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How’s the 7th injector? Your getting good heat so it should be good. Sometimes they will dump fuel and not spray a mist. I wonder if the truck needs an update or something. Sensors seem be telling the truck regens are complete but they clearly are not. 

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we thought of the 7th injector, may need to do a flow test on it. we ran the engine with it unbolted thinking it was dumping fuel in but it is not.

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So this is tough because you say it runs great other then the filter issue and your getting good temps. Also the truck is saying it’s completing regens but it’s not…

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That delta p sensor could be an issue. One way to find out is get PTT going and turn the key on. If you have a reading other then zero it’s bad. So I have found. We had one plug a dpf due to egr valve and that sensor 

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Posted (edited)

There’s a few other guys on here that will be more then likely able to help you. It’s just so hard to do over the computer on these MPs. The possibilities are endless. 

Edited by Onyx610
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1 hour ago, Vmac3 said:

Another thing that causes excessive black smoke that a lot of techs overlook (self included) is the engine air filter.

I had a MR US10 emissions where it did the exact same thing. Checked everything under the sun and days into this, I noticed the air intake pipe was behind the exhaust pipe sucking in the soot that was belching out of the exhaust. The air filter must of weight 45lbs. The air filter was never changed which caused the excessive soot. I changed the air filter, repositioned the air intake and never saw the truck come in for the same problem.

Don't know if this will help. 

V

Yup REAL Good point!  guys tend to migrate to that computer screen and get absorbed in whats there with out thinking about the simpler stuff!

Start at the begining ! The instructions probably  don't even mention that one!

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no boost leaks, checked and cleaned the EGR differential sensor tubes going to it. sensor replaced a couple months before all this happened. it came with a pigtail and I wired it matching how the old one was wired. maybe i need to check the wiring. VGT test passed. doing an EGR test next also.

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14 hours ago, Wasteman1 said:

no boost leaks, checked and cleaned the EGR differential sensor tubes going to it. sensor replaced a couple months before all this happened. it came with a pigtail and I wired it matching how the old one was wired. maybe i need to check the wiring. VGT test passed. doing an EGR test next also.

Rey bro you say the vgt past the  test? There is / was a test in the ptt program for turbo effort did you try that ? The turbo can past the sweep test but still be sticking! Fuel pressure at the 7th injector OK? fine to have flow is  the pressure there? Just some stuff our guys  look for when we get issues like this!

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Being it a 2009. There has been at least 2 ( possible 3) EGR valve updates . More importantly there has been many EGR Diff pressure sensor/venturie updates.  If the EGR diff sensor ports are clogged then the engine ecm sees no flow even though there is flow. The engine ecm then commands the EGR valve to open more to try to get flow , this over soots the DPF 

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Out of curiosity is the DRV something to consider? Could these get stuck open and essentially creating an internal boost leak? Never had any issues with them but wasn’t sure if it was a possibility? 

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