Goddy454 Posted December 5, 2023 Share Posted December 5, 2023 Good Morning, I have a MP8 with a hard start after sitting, cranks long but will eventually start, this has been going on for some time. Truck runs fine once running but after sitting overnight or for a few hours its tough to start. I have run the test with the clear tubing from the front of the head to the tank with the return port in the fuel filter housing plugged off. The test instructions say to look for heavy foam or large bubbles. I do not see any large bubbles but do see foam. I have never run this test on another truck so I cant determine if this foam is considered typical or abnormal. I would appreciated any comments from anybody on their thoughts. Also according to the instructions they say that the primer pump is not a source of air in the fuel system. I did notice that the fitting to the right of the primer pump knob is leaking when I pump the handle, any thoughts on that. Thanks for any help. Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/ Share on other sites More sharing options...
Goddy454 Posted December 5, 2023 Author Share Posted December 5, 2023 Here is a pic of the leak I am referring to, in the pic its on the left. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-542955 Share on other sites More sharing options...
Joey Mack Posted December 5, 2023 Share Posted December 5, 2023 Looks airy to me.. I bet inside the tanks looks like beer suds... Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-542964 Share on other sites More sharing options...
Goddy454 Posted December 8, 2023 Author Share Posted December 8, 2023 Where its coming out into the tank looks ok, really nothing. Was trying to get a pic but couldn't get a good one. Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-543148 Share on other sites More sharing options...
Mackpro Posted December 8, 2023 Share Posted December 8, 2023 Here the bulletin, click on view file . https://macktrucks.vg-emedia.com/ProductDetail.aspx?ProductId=11698 Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-543152 Share on other sites More sharing options...
Goddy454 Posted December 10, 2023 Author Share Posted December 10, 2023 Thats the bulletin I've been using all along on this diagnosis. Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-543226 Share on other sites More sharing options...
Miami Cossack Posted December 10, 2023 Share Posted December 10, 2023 That would be what they call "Heavy Foam". A little bit isn't much to worry about but you have a lot. 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-543250 Share on other sites More sharing options...
Goddy454 Posted December 17, 2023 Author Share Posted December 17, 2023 Thank You Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-543583 Share on other sites More sharing options...
Goddy454 Posted December 24, 2023 Author Share Posted December 24, 2023 I ended up replacing the fuel filter head assembly along with all the sealing washers and all is well. Thanks 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-544010 Share on other sites More sharing options...
Joey Mack Posted December 24, 2023 Share Posted December 24, 2023 thanks for posting the repair.. Jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73616-2013-gu813-mp8-hard-start/#findComment-544012 Share on other sites More sharing options...
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