1wonton Posted July 4, 2023 Share Posted July 4, 2023 My '60 B model loose prime after a day or so. Checked all the lines for leaks but can't find any. Could I install a fuel pump in-line or maybe a check valve. If a check valve where should it be located? Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/ Share on other sites More sharing options...
Geoff Weeks Posted July 4, 2023 Share Posted July 4, 2023 Coupla ideas. I had a truck that had a problem, it turned out the Strato-flex line from the tank to the pump had leaks, wouldn't leak fuel but would suck air into the fuel. When it finely got bad enough the truck would start to run like a clogged fuel filter. So if your suction line hasn't been changed in years, that is something to try. I also added a check valve at the tank. It is important not to increase the restriction in the suction line, I used a "swinging disk" style check as they have very low restriction in the forward direction. God, I miss Glenn Akers, he was a wiz on stuff like this. Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534140 Share on other sites More sharing options...
Geoff Weeks Posted July 4, 2023 Share Posted July 4, 2023 Also check you are using the correct fuel filter for the application, and any sealing washers/ O rings that come with the filter are used. Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534141 Share on other sites More sharing options...
Geoff Weeks Posted July 4, 2023 Share Posted July 4, 2023 If it is Detroit powered, it need the return to the tank submerged in fuel. Tanks for other engine may just have the return dump in the top, a Detroit needs in under the fuel (it will back siphon air when not running if return is above fuel level.) Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534142 Share on other sites More sharing options...
mrsmackpaul Posted July 4, 2023 Share Posted July 4, 2023 You need to understand how the fuel system works But as a general rule, if you loose prime when its running the the leak is on the supply line If you loose prime when its sitting the leak is on the return to tank side Try putting the fuel system under some slight pressure using your work shop air compressor A piece of rubber inner tube with a tyre valve fitted over the filler cap hole held on with a hose clamp works well Make sure you wind the air pressure down as low as it goes, the vent on the tank should stop to much pressure building Remember every little hose between the in injectors is a place to leak And also remember you wont see any leaks on the return to tank side as they are all under vacuum not pressure so there won't be a wet spot Good luck Paul 2 Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534159 Share on other sites More sharing options...
doubleclutchinweasel Posted July 5, 2023 Share Posted July 5, 2023 21 hours ago, Geoff Weeks said: God, I miss Glenn Akers, he was a wiz on stuff like this. Amen, Geoff. Quote "Eagles may soar, but weasels don't get sucked into jet engines." Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534220 Share on other sites More sharing options...
1wonton Posted July 5, 2023 Author Share Posted July 5, 2023 All good ideas. What is a good brand of 3/8" flexible braided hose? I see many different brands (Amazon, Summit) but some seem to have problems. Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534225 Share on other sites More sharing options...
Geoff Weeks Posted July 5, 2023 Share Posted July 5, 2023 It doesn't really matter. The local hose shop switched to Gates, I'm not a great fan of, but had no trouble with the hose, it was more the range of fittings, that were a problem after the switch. Just want something rated for diesel, with a wire braid so it can't collapse. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534229 Share on other sites More sharing options...
mrsmackpaul Posted July 6, 2023 Share Posted July 6, 2023 Ryco is the brand for me, but you wont get that in the states Gates is or was a good brand, still arefor belts etc Paul Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-534300 Share on other sites More sharing options...
1wonton Posted July 19, 2023 Author Share Posted July 19, 2023 Checked all fuel lines to and from the pump but still found no leaks. Truck will start and run briefly after sitting a day or so, then dies. Could there be a leak inside the pump itself? I tried forcing compressed air from the tank but found no leaks. Would a check valve be needed? Quote Link to comment https://www.bigmacktrucks.com/topic/73005-losing-prime/#findComment-535174 Share on other sites More sharing options...
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