wacopaving Posted January 31, 2020 Share Posted January 31, 2020 Hey guys, Now that the electrical problem is fixed I have another issue. I have an EM7 engine in this truck and for some reason it’s losing its prime. Replaced the check valve in the side of the block. Checked all of the injectors by taking the injector lines loose and seeing if the cylinder die out properly. Checked all fuel lines and filters, which are all clear of debris and trash. The only thing left that I think it can be is the primer pump. It’s a super hard start in the morning but usually the rest of the day is okay. If you let the truck sit too long it loses its prime and then you have to prime the shit out of it and crank it over a bunch to get it going. Any ideas of what it could be? Quote Link to comment https://www.bigmacktrucks.com/topic/60787-1999-mack-rd690s-keeps-losing-its-prime/ Share on other sites More sharing options...
fjh Posted February 1, 2020 Share Posted February 1, 2020 (edited) If the engine has a plastic return line to the head I would check to see it isn't worn thru or the ends arn't loose on the barbs also check the jumper line between the valve covers the orings sometimes leak! Injector orings can sometimes cause this issue as well!and of coarse the transfer pump! check the easy cheap stuff first the pump ain't cheap! Edited February 1, 2020 by fjh 1 Quote Link to comment https://www.bigmacktrucks.com/topic/60787-1999-mack-rd690s-keeps-losing-its-prime/#findComment-441736 Share on other sites More sharing options...
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