Popular Post h67st Posted Thursday at 12:05 PM Popular Post Share Posted Thursday at 12:05 PM I’ve been fighting a starting issue since I got this truck back together in 2023, of course I only drive it about 6 times a year so I haven’t pushed too hard to fix it. It would start easily but then run out of fuel and I would have to crank it for a few seconds to get it going again. Also the hand primer wouldn’t pick up fuel unless I poured fuel in the inlet line. I went through the fuel lines, check valves, and replaced the hand primer. Then a couple of weeks ago I was reading what other guys did to fix theirs, and one guy on here (now I can’t find the post) said the overflow valve would cause this problem. That is the return tee at the back of the injection pump. I never had any experience with those; I looked at my old fuel system repair manual and it said that valve could cause issues with starting and low power. The spec on mine is 15 psi; I tested it and it held less than 10 psi. The one for the 673 is 697GC15, but that is NLA. The number for the E6 is 697GC123 and it’s the same configuration (1/4 x 1/4 x 1/8 NPT) so I bought one from PAI (no. 801090, $100). I tested the new one and it holds 20 psi. I installed it and now the truck starts and runs correctly. It’s frustrating to dink around with something for so long but I’m glad it’s fixed! 5 Quote Link to comment https://www.bigmacktrucks.com/topic/75365-overflow-valve-starts-and-dies/ Share on other sites More sharing options...
mowerman Posted Thursday at 08:41 PM Share Posted Thursday at 08:41 PM haha,,,,stuff drives you nuts,,,mine does the same thing ,,,but i know what it is,just havent done anything with it yet,,,glad you got it figured out 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75365-overflow-valve-starts-and-dies/#findComment-572765 Share on other sites More sharing options...
Vladislav Posted Thursday at 08:59 PM Share Posted Thursday at 08:59 PM Glad to hear the problem is solved. That old valve at the right of the picture - can't you take it apart and check the inside out? There must be a sort of spring and a plunger/ball/a diaphragm which could be bad. 1 Quote Никогда не бывает слишком много грузовиков! leversole 11.2012 Link to comment https://www.bigmacktrucks.com/topic/75365-overflow-valve-starts-and-dies/#findComment-572769 Share on other sites More sharing options...
h67st Posted Friday at 12:06 PM Author Share Posted Friday at 12:06 PM On 4/3/2025 at 8:59 PM, Vladislav said: Glad to hear the problem is solved. That old valve at the right of the picture - can't you take it apart and check the inside out? There must be a sort of spring and a plunger/ball/a diaphragm which could be bad. Expand I figured I could probably replace the spring but the valve/seat is worn so I went ahead and replaced it. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/75365-overflow-valve-starts-and-dies/#findComment-572800 Share on other sites More sharing options...
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