DarrylMueller Posted August 4, 2019 Share Posted August 4, 2019 This problem is a leak down of fuel when parked or not running. This truck usually starts right away. The last time I used it I did have some issue that it turned over a few extra times when I turn it off. So this is something I was expecting. I have let it set several months and it will not start, so I am sure there is air in the fuel system. I am sure that I could get it going with starting fluid but I would like to fix it. There must be a "check valve" or something like that stuck open and it is allowing the fuel to drain back to the tank. Yes it's an old truck 1976 but in great shape and I have owned it for most of its life. Hoping there is a veteran Mack mechanic that can help solve the problem. Quote Link to comment https://www.bigmacktrucks.com/topic/58442-v8-endt-866-fuel-system-leak-down-issue/ Share on other sites More sharing options...
fjh Posted August 4, 2019 Share Posted August 4, 2019 (edited) There is drain back valve in the rear right side of the fuel pump block next thev governor houseing under the shut down lever it’s real hard to remove it’s usually a hammer and punch show it’s round with screw driver slots on it Allen screw in the middle!it likely needs orings replaced have an oring kit handy! Edited August 4, 2019 by fjh 1 Quote Link to comment https://www.bigmacktrucks.com/topic/58442-v8-endt-866-fuel-system-leak-down-issue/#findComment-429365 Share on other sites More sharing options...
DarrylMueller Posted August 5, 2019 Author Share Posted August 5, 2019 Wow, Thanks for the come back, that is what I was looking for. Quote Link to comment https://www.bigmacktrucks.com/topic/58442-v8-endt-866-fuel-system-leak-down-issue/#findComment-429405 Share on other sites More sharing options...
DarrylMueller Posted September 8, 2019 Author Share Posted September 8, 2019 I took a picture of the area. Is the hex plug were the drain back valve is? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/58442-v8-endt-866-fuel-system-leak-down-issue/#findComment-431682 Share on other sites More sharing options...
JoeH Posted September 8, 2019 Share Posted September 8, 2019 On 8/4/2019 at 2:51 PM, fjh said: There is drain back valve in the rear right side of the fuel pump block next thev governor houseing under the shut down lever it’s real hard to remove it’s usually a hammer and punch show it’s round with screw driver slots on it Allen screw in the middle!it likely needs orings replaced have an oring kit handy! Bump Quote Link to comment https://www.bigmacktrucks.com/topic/58442-v8-endt-866-fuel-system-leak-down-issue/#findComment-431685 Share on other sites More sharing options...
fjh Posted September 8, 2019 Share Posted September 8, 2019 That be it! The big round thing screws in it has orings on it! the drain valve inside it has a spring behind a needle valve same as the E6 1 Quote Link to comment https://www.bigmacktrucks.com/topic/58442-v8-endt-866-fuel-system-leak-down-issue/#findComment-431687 Share on other sites More sharing options...
DarrylMueller Posted September 9, 2019 Author Share Posted September 9, 2019 Thanks I just want the right place. Quote Link to comment https://www.bigmacktrucks.com/topic/58442-v8-endt-866-fuel-system-leak-down-issue/#findComment-431734 Share on other sites More sharing options...
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