OJ Avery Posted May 3, 2018 Share Posted May 3, 2018 I have a 2012 with a mp7 2010 emissions (spark assist) the problem I'm having is it looses its fuel prime over the weekend, sometimes overnight. I replaced the fuel filter head and filters, one check ball was sticking. Still did it. Replaced the "pressure regulator" on the return side on top of the head, still did it. Did an air in fuel test and it looked great. Did a warm hold function, that was good torque was 60ft# at idle. Did a cylinder balance test and #2 was off the most (+23), #6 was next at -20, # 3 -19. This vehicle only has 37k on it. But its a paint truck, really heavy and really slow driving. Do I have an injector leaking down causing it to loose its prime? Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/ Share on other sites More sharing options...
fjh Posted May 3, 2018 Share Posted May 3, 2018 Yes most common failure is injector cup injector seat failure 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398169 Share on other sites More sharing options...
OJ Avery Posted May 3, 2018 Author Share Posted May 3, 2018 Thanks fjh, I was looking for confirmation, just so low miles, a little hard to believe. Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398170 Share on other sites More sharing options...
Mackpro Posted May 3, 2018 Share Posted May 3, 2018 I just put cups in a 2017 pre-common rail engine last week. It can happen to any of them. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398175 Share on other sites More sharing options...
OJ Avery Posted May 4, 2018 Author Share Posted May 4, 2018 injectors are out, 2 of them show significantly more carbon than the rest. That's just a lot of $ for so little miles. Glad its not mine Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398218 Share on other sites More sharing options...
fjh Posted May 4, 2018 Share Posted May 4, 2018 Mackpro have you had any cup / injector failures on the common rail units in you area yet? Not a one here yet ! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398225 Share on other sites More sharing options...
RobM626 Posted May 4, 2018 Share Posted May 4, 2018 4 hours ago, OJ Avery said: injectors are out, 2 of them show significantly more carbon than the rest. That's just a lot of $ for so little miles. Glad its not mine I just did mine on an 08 mp7. Around 50,000 miles.. mack talked me into replacing with the updated cups and injectors 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398231 Share on other sites More sharing options...
Mackpro Posted May 4, 2018 Share Posted May 4, 2018 5 hours ago, fjh said: Mackpro have you had any cup / injector failures on the common rail units in you area yet? Not a one here yet ! Nope . Other than at school, we have never pulled the valve cover off a common rail engine here. A few Particulate matter sensors and software have been the only problems so far . And we have several running around here. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398238 Share on other sites More sharing options...
Mack Technician Posted May 4, 2018 Share Posted May 4, 2018 6 hours ago, fjh said: Mackpro have you had any cup / injector failures on the common rail units in you area yet? Not a one here yet ! 1 hour ago, Mackpro said: Nope . Other than at school, we have never pulled the valve cover off a common rail engine here. A few Particulate matter sensors and software have been the only problems so far . And we have several running around here. The instructor at Volvo training said the elimination of graphite paste in injector assembling was a move to stop improper factory installation. They suspected the paste would not displace fast enough to react to rapid installation of assembly machine. The lubricant would not crawl out, get hydro-locked, then create a false torque that loosened. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398240 Share on other sites More sharing options...
Mackpro Posted May 4, 2018 Share Posted May 4, 2018 A few months back they had us quit using graphite paste and only rub some oil on the injector seating area. Last time I checked, we are back to using graphite paste but only a very very small amount. I need to pull it back up in Impact and see if they changed their minds again! Lol 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398243 Share on other sites More sharing options...
fjh Posted May 6, 2018 Share Posted May 6, 2018 (edited) There torquing method is out to lunch in my mind tightening and loosening makes little sense in my mind how ever with such a wimpy bolt this method may be needed!we did some the other day we used oil! WHAT ever! any assembly procedure alterations will not totally correct a poor hold down design! Edited May 6, 2018 by fjh 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398379 Share on other sites More sharing options...
Mackpro Posted May 6, 2018 Share Posted May 6, 2018 Sad thing is Volvo has been using this same set up back in the D12 days(12-15 years ago or more). 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398397 Share on other sites More sharing options...
fjh Posted May 6, 2018 Share Posted May 6, 2018 2 hours ago, Mackpro said: Sad thing is Volvo has been using this same set up back in the D12 days(12-15 years ago or more). Definition of crazy ! Doing the same thing over and over and getting the same result! 😠 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398403 Share on other sites More sharing options...
OJ Avery Posted May 8, 2018 Author Share Posted May 8, 2018 I did the injectors and it doesn't lose its prime overnight. Thanks for the input guys, I really appreciate it. This forum is gold to me as I work on DOT trucks with little factory training. We've been given a decent supply of specialty tools so doing all repairs is possible but a little short on diagnostics. We've been using the graphite paste on all our injector jobs. We do probably more than average amount of injectors because of the truck use. They're plow trucks so they're over loaded with iron and salt and usually travel about 35-40 mph. we don't usually see a set go past 100,000 miles. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398534 Share on other sites More sharing options...
1965 Posted May 8, 2018 Share Posted May 8, 2018 1 hour ago, OJ Avery said: . we don't usually see a set go past 100,000 miles. That’s a shame!! Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398537 Share on other sites More sharing options...
OJ Avery Posted May 8, 2018 Author Share Posted May 8, 2018 It is a shame. we have an 08 tractor that is mainly over the road and that truck has 225000 on it now with oe injectors. How they get used makes a huge difference. Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398542 Share on other sites More sharing options...
Mack Technician Posted May 9, 2018 Share Posted May 9, 2018 Same to be said about our 2 low horsepower Volvo D13J engines (aka MP8). Different application. They never needed cups at the 330HP setting. Checked one today at nearly 17K hours and all originally cups and injectors. Actually very few engine issues altogether. Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398574 Share on other sites More sharing options...
OJ Avery Posted May 9, 2018 Author Share Posted May 9, 2018 The MP8 would have been a much better application here, but when you work for the state...... Quote Link to comment https://www.bigmacktrucks.com/topic/53285-mp7-looses-its-prime/#findComment-398579 Share on other sites More sharing options...
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