steeler Posted November 22, 2020 Share Posted November 22, 2020 Hopefully somebody can lead me in the right direction here. I'm working on a 2013 Mph that is black smoking and throwing codes for cylinder #4 cylinder balance, and cylinder #4 misfire. I replaced #4 injector, that didn't help at all. I've ran compression test which all cylinders checked perfect. When I do the cylinder balance test with tech tool, #4 is way overfueling. Cylinders 1 and 5 are near zero in the balance test, 2 and 6 are about -17, and #4 is climbing pretty fast at +56. #3 is -25. Not sure where to go other than throwing 5 more injectors at it, but that would be a pricey strikeout! Quote Link to comment https://www.bigmacktrucks.com/topic/65027-2013-mp7-over-fueling-problem/ Share on other sites More sharing options...
Mackpro Posted November 23, 2020 Share Posted November 23, 2020 I remember having lots of issues with a certain emission year group of MP7’s. I believe it was around the 14-15 year models. Engines would have lots of injector codes and not running smoothly. The wiring harness was rubbing the top front of the air compressor. Mack sent out a bulletin it at the time. It’s worth a shot, I remember using a long pry bar to lift up the harness and a mirror to look under it for bare wires , it was hard to reach . Quote Link to comment https://www.bigmacktrucks.com/topic/65027-2013-mp7-over-fueling-problem/#findComment-464260 Share on other sites More sharing options...
steeler Posted November 23, 2020 Author Share Posted November 23, 2020 29 minutes ago, Mackpro said: I remember having lots of issues with a certain emission year group of MP7’s. I believe it was around the 14-15 year models. Engines would have lots of injector codes and not running smoothly. The wiring harness was rubbing the top front of the air compressor. Mack sent out a bulletin it at the time. It’s worth a shot, I remember using a long pry bar to lift up the harness and a mirror to look under it for bare wires , it was hard to reach . Yup, I've changed many harnesses for that problem. Never had one at like this, but I'll definitely be checking that. Another thing I thought was strange was that the suspect cylinder had a different part number injector, but it crossed to the same part, except it showed as a new injector and not a reman. None of them looked like they had been replaced recently though. Quote Link to comment https://www.bigmacktrucks.com/topic/65027-2013-mp7-over-fueling-problem/#findComment-464261 Share on other sites More sharing options...
steeler Posted November 27, 2020 Author Share Posted November 27, 2020 Problem found! Long story short is original complaint was low power and black smoke. After replacing the injector I found 4 intake manifold bolts broken and cracked manifold. That didn't help the smoking. Went ahead and pulled dpf and found it completely melted out. O don't have any idea how this thing regened normally and didn't have a single dpf code in it. But oh well! Quote Link to comment https://www.bigmacktrucks.com/topic/65027-2013-mp7-over-fueling-problem/#findComment-464461 Share on other sites More sharing options...
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