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Rockwell

Mp8 sudden momentary loss of boost pressure

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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. 

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Posted (edited)

Check and clean your battery/starter connections Bad grounds do weird things ! Check the cheap and easy stuff first!

Edited by fjh
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Posted (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 by Rockwell

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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. 

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