fg61 Posted December 31, 2011 Share Posted December 31, 2011 Hi guys I have a 2009 gu713 tandem dump with a mp7. I am having some sporadic starting issues. Happens every so often cold and warm. It cranks cranks . Sometimes it takes 3 of 4 tries for it to start. Truck has 35,000 miles. Any feed back would help. Thanks Quote Link to comment Share on other sites More sharing options...
Fran3682821 Posted December 31, 2011 Share Posted December 31, 2011 I got the same motor in my truck MP7 the first thing you should do is take it to a dealer and get a bubble test done for the injection cups that is a common problem for these motors that causes the motor to loose some power and hard to start. But once what happened to me I had been to the mack dealer for a check up performed the bubble test and everything was fine. The following week my truck on occasion maybe twice a week would be hard to start like yours 3 to 4 tries to get it to start. I left it alone and then the following week a sensor for the fuel pressure installed in the filter housing coming out of the top of my fuel filter it resembles a rubber diaphram completely let go fuel began pouring out the top of the fuel filter housing. Once I changed that I never had a problem with the truck starting. I think air was getting in by a small crack in the rubber diaphram making air bubbles. I'am not a top expert but thats what happened to me. Quote Link to comment Share on other sites More sharing options...
shortstack Posted December 31, 2011 Share Posted December 31, 2011 As already mentioned, injector cups were a problem on these engines. Once updated they don't seem to give anymore problems. That would be my guess. Trey Quote Link to comment Share on other sites More sharing options...
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