Deere Mack Posted July 21, 2014 Share Posted July 21, 2014 Hello friends! I hope everyone is doing well, it's been a while. Started haveing some trouble with the 1979 RD685S dump truck that has a 1973 237 engine. Once it sits a while, it'll start right up run fine for a few sec and go dead. After that it's very hard to start to the point of draining batteries. But once it starts back up it'll run all day and restart with no problem until it sits for a day or so. It does have new filters. Any tips would be appreciated! Quote Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/ Share on other sites More sharing options...
farmer52 Posted July 21, 2014 Share Posted July 21, 2014 Sounds like a check valve in the fuel supply line....letting the fuel drain back to the tank. Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-253574 Share on other sites More sharing options...
Deere Mack Posted July 21, 2014 Author Share Posted July 21, 2014 Sounds like a check valve in the fuel supply line....letting the fuel drain back to the tank.Is that on the pump side or return? Quote Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-253575 Share on other sites More sharing options...
farmer52 Posted July 21, 2014 Share Posted July 21, 2014 Most fuel systems have a check valve on the supply side, I suspect it is located in the lift pump. I am sure someone on BMT is more knowledgeable than me. If I am wrong someone will hopefully correct my mess.Could also be a bad "seal" on the fuel filter.Either way it sounds like the fuel system is losing "prime" when sitting for extended time. Quote Ken PRR Country and Charter member of the "Mack Pack" Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-253585 Share on other sites More sharing options...
ThaddeusW Posted July 22, 2014 Share Posted July 22, 2014 Sounds close to my problem. Though, I never touched my filters before my problem.As other has said sounds like you are loosing prime from the pump to the tank. I would unscrew the new filters and clean the seal and the face of the filter mount to ensure there is a tight seal. Any air between the tank and lift pump and you will lose prime. It is also possible that perhaps the primer handle will let some air into the lines as well, my primer handle on my 673 will bubble and leak a bit of fuel when priming. Though I would look at the filer seal first. Quote -Thad What America needs is less bull and more Bulldog! Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-253651 Share on other sites More sharing options...
Deere Mack Posted July 22, 2014 Author Share Posted July 22, 2014 Thanks for the tips! I'm very suspicious of the fuel filter now that you mention it. Seems it all started shortly after I replaced them, but I also filled the tanks completely up probably for the first time in a while. Was thinking some rust might have give me some trouble, but it runs to good when it starts. Its definately loosing prime as it sits. Never had that to happen on a fuel filter. I did look for fuel leaks and didn't notice any. I'll look into it and let you know. Quote Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-253653 Share on other sites More sharing options...
Deere Mack Posted July 23, 2014 Author Share Posted July 23, 2014 Going to have to wait until I can get extra filters. I let a local mechanic I've used before service the truck and he installed the filters. They are on so tight that I'll probably damage them trying to remove. This makes me think even more that the seals could be pinched or rolled. Quote Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-253765 Share on other sites More sharing options...
gearhead204 Posted July 23, 2014 Share Posted July 23, 2014 sounds like your on the right track you definitely have a air leak on the fuel system you might also put about 7psi or less into the tank and watch for drips or sweating on the hoses or lines Quote Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-253778 Share on other sites More sharing options...
altonforbus Posted August 3, 2014 Share Posted August 3, 2014 I have found the seat on the fuel overflow valve either with a pin hole in it or just not seating to cause this exact problem on more than a few occasions. Quote Link to comment https://www.bigmacktrucks.com/topic/36424-1973-237-engine-fuel-problems/#findComment-254925 Share on other sites More sharing options...
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