Rockwell Posted January 9, 2019 Share Posted January 9, 2019 Hello, 2011 Mack CXU613 MP8-445 600,000 miles(10speed) Motor intermittently stumbles or jerks on hard pull when calling for boost. Then returns to normal. When the motor stumbles, my boost pressure goes from let's say 33 to flat line. Not zero, just two dashes as if there is no reading or boost whatsoever. Looks like this... 33... Motor stumbles and display reads - -. Then it returns to normal. No codes being thrown. No other symptoms. Pressure Sensor? Actuator? Any ideas would be greatly appreciated! Truck had had new injectors/cups and fuel filters are good. Even at idle, boost pressure will go from 2 or 3 psi to - - momentarily on center display. Quote Link to comment Share on other sites More sharing options...
fjh Posted January 9, 2019 Share Posted January 9, 2019 (edited) Check and clean your battery/starter connections Bad grounds do weird things ! Check the cheap and easy stuff first! Edited January 9, 2019 by fjh 1 Quote Link to comment Share on other sites More sharing options...
Rockwell Posted January 9, 2019 Author Share Posted January 9, 2019 (edited) Thank you fjh, what's funny is Mack installed a new starter, got the truck back and had this problem on first run out. Awefully coincidental. All starter wires bright and tight. Edited January 9, 2019 by Rockwell Quote Link to comment Share on other sites More sharing options...
Rockwell Posted January 12, 2019 Author Share Posted January 12, 2019 Just in case it helps another down the road... Problem Solved. Engine harness behind engine fan had a short in the 5. volt sensor supply wire. 1 beer for fjh! You called it. 1 Quote Link to comment Share on other sites More sharing options...
Rilex Posted January 8, 2020 Share Posted January 8, 2020 Hello Did you ever fixed this problem. I have 2008 CHU 613 with this problem.I replaced sensors for turbo shaft speed, turbo temperature sensor, but problem is still there. Momentarily will lose boost and then goes normally for miles.This happens mostly up hills under load. Quote Link to comment Share on other sites More sharing options...
mp8_macky Posted February 3, 2020 Share Posted February 3, 2020 I recommend that you check EGR valve that can also be an issue, if it is sticking. Do you check for codes? Try cleaning the boost pressure sensor (i doubt that it will help, but you can try). Quote Link to comment Share on other sites More sharing options...
Chase1210 Posted August 26, 2023 Share Posted August 26, 2023 On 1/12/2019 at 5:06 PM, Rockwell said: Just in case it helps another down the road... Problem Solved. Engine harness behind engine fan had a short in the 5. volt sensor supply wire. 1 beer for fjh! You called it. i have this same issue with my mp7. can anyone be more specific about where to find this wire? what color it is ? anyone have a diagram? thanks! Quote Link to comment Share on other sites More sharing options...
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