Old_DM Posted September 14 Share Posted September 14 Have put off changing the fuel filters for way to long on my DM685 (1971) due to worries about getting it primed. It was well used and abused when I got it for cheap, but the fuel lines all look original and correctly plumbed. Suction through the coarse filter, into the lift pump / primer then out to the fine filter and into the injection pump. My question is, when I remove the filters, will the main injection pump wind up with air in it? Especially after removing the fine filter. I plan on filling the new filters before installation. Will I be looking at having to loosen the injection line couplings at the injectors to purge air from the lines or is the primer on the lift pump used to purge air through the top of the main injection pump housing? Also, are the old factory fuel fittings all 45 degree flares on these old trucks, or some long abandoned standard? 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/ Share on other sites More sharing options...
mowerman Posted September 14 Share Posted September 14 there is plenty of sources out there and yes they are all available dealer does not sell them on the roll anymore i just changed mine went to a hydraulic line shop in town got everything,,,and no you dont have to touch pump or injectors if you have a problem with priming after wards spin it over a few times with starting fluid untill it runs on its own good luck and yes the ends are reusable,,,bob 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558509 Share on other sites More sharing options...
Popular Post mowerman Posted September 14 Popular Post Share Posted September 14 if its very stubborn and still wont catch i made this up got everything at home depot to blow air into the fuel tank only around 20 lbs,,,the chrome thing is a fence post cap drilled a hole and put in this air nipple works like a champ,,,bob 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558510 Share on other sites More sharing options...
mowerman Posted September 14 Share Posted September 14 and yes i also have a 66DM and i would swear all my lines were original,although i dont know if thats possible 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558511 Share on other sites More sharing options...
Old_DM Posted September 14 Author Share Posted September 14 Thanks for the info. Love the air tank pressurizer, great idea. Hopefully I won't have to go that route. On double fuel tank set ups, is there a check valve between the main tank and the feed from the aux tank? I have a weird looking right angle fitting poking out of the aux tank before the line that connects over to the main tank. Are these set up to only allow draining from the aux tank towards the main? Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558518 Share on other sites More sharing options...
mowerman Posted September 14 Share Posted September 14 I am not sure what you’re talking about but I’m sure other guys will chime in and yes, I don’t think you’re gonna have to need that device. Just an option as I said I bought everything at Home Depot right off the shelves…. Right now mine keeps losing prime so I have to blow it just about every time I start it so far I’ve only changed the oil lines. Haven’t done anything with any other others yet…. It was starting with a little ether now that’s not even doing it after one week. It’s already got air in it. And I usually start every Saturday. Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558519 Share on other sites More sharing options...
mowerman Posted September 14 Share Posted September 14 I’m thinking possibly fuel return line Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558520 Share on other sites More sharing options...
mechohaulic Posted September 15 Share Posted September 15 3 hours ago, Old_DM said: Thanks for the info. Love the air tank pressurizer, great idea. Hopefully I won't have to go that route. On double fuel tank set ups, is there a check valve between the main tank and the feed from the aux tank? I have a weird looking right angle fitting poking out of the aux tank before the line that connects over to the main tank. Are these set up to only allow draining from the aux tank towards the main? not sure of the "weird looking fitting". picture be helpful . should only be a cross over line from one tank to other, new standards don't allow cross over line located on angle iron connecting the two tanks lower to ground due to hazard of road debris ripping line causing fuel leak. additional fitting on tank may be for access to fuel:: asphalt haulers had them for getting fuel to spray tail gates . by pictures I would recommend some cans of brake clean and spray filter bases and primer pump area before removal of filters.. also one filter change at a time. clean// remove/ install new filter. possibly another cut back , but the new filters had a plastic cover which i put back on the new filled filter to slip in to position for reinstall. helped keep out dirt.smaller loss of fuel when tipping new filled filter in to spot. then remove the cover= install filter (2). hopefully hand primer works after two filters changed. 2 Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558531 Share on other sites More sharing options...
Popular Post terry Posted September 15 Popular Post Share Posted September 15 5 hours ago, Old_DM said: Have put off changing the fuel filters for way to long on my DM685 (1971) due to worries about getting it primed. It was well used and abused when I got it for cheap, but the fuel lines all look original and correctly plumbed. Suction through the coarse filter, into the lift pump / primer then out to the fine filter and into the injection pump. My question is, when I remove the filters, will the main injection pump wind up with air in it? Especially after removing the fine filter. I plan on filling the new filters before installation. Will I be looking at having to loosen the injection line couplings at the injectors to purge air from the lines or is the primer on the lift pump used to purge air through the top of the main injection pump housing? Also, are the old factory fuel fittings all 45 degree flares on these old trucks, or some long abandoned standard? Just fill filters completely up, and pump primer till hard, should start, might miss for a few seconds but should clear up. Terry 4 Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558535 Share on other sites More sharing options...
Freightrain Posted September 19 Share Posted September 19 If the primer is dry, you can unscrew it from the base and put some fuel in it to get the check valves working. As you pump it, after a short time it will get tougher and that tells you that it is primimg. I usually go another 30 secs and it will light off pretty easy. Might chug or two but will clear up. 2 Quote Larry 1959 B61 Liv'n Large...................... Charter member of the "MACK PACK" Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558774 Share on other sites More sharing options...
skydawg Posted September 21 Share Posted September 21 I don`t have a hand primer on my ENDT673,so am planning to use Bob`s method.Bob,how long do you keep pressure on that tank? Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558841 Share on other sites More sharing options...
glenbjackson Posted September 21 Share Posted September 21 i like air adapter idea as well, think ill make one. on truck plumbing i suggest installing hand primer on lift pumps as well as a hand pump near the tank. i have this setup on my CM soon all my trucks. Story on how i came to that setup....A sneaky leaky hand priming pump left me stranded once. very very old plastic hand primer pump allowing air into system. Plastic pump was replaced and new one trying to pull fuel on a dryish??\open system through filters didnt work out. Learning from that i just make my fuel systems able to get prime whereever im at. Any patching to get going on side of road may need fuel system priming. the one near tank is just same hand primer pump at lift pump, with two check valves(one on either side of tee-in hand pump), with a ball valve in parallel(cut off only for priming) Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558844 Share on other sites More sharing options...
mowerman Posted September 21 Share Posted September 21 13 hours ago, skydawg said: I don`t have a hand primer on my ENDT673,so am planning to use Bob`s method.Bob,how long do you keep pressure on that tank? i leave it connected for around 10 minutes,,,,ill be starting mine soon,,,ill probably wind up doing the same thing,,,,i have a hand pump,,,but it dont work worth a shit...bob Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558859 Share on other sites More sharing options...
mowerman Posted September 21 Share Posted September 21 if your going to put one together,,,i put gaskit sealer on the nipple before i screwed it in the the fence post cap,,,,good luck,,,bob Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558860 Share on other sites More sharing options...
skydawg Posted September 21 Share Posted September 21 I`m low tech...an old piece of tube w/ the valve and a hose clamp to seal it to the tank. Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558871 Share on other sites More sharing options...
Popular Post Full Floater Posted September 21 Popular Post Share Posted September 21 I have a Walbro FRB series lift pump installed on the frame rail between the tank and the lift pump. It's a "pass thru" design that when not energized, the factory lift pump will simply pull thru it. I have it on a manual toggle switch so in the event of emergency air intrusion on the side of the road or filter change or whatever, there is no question that I will be able to get it to prime up fast 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558873 Share on other sites More sharing options...
mowerman Posted September 21 Share Posted September 21 5 hours ago, skydawg said: I`m low tech...an old piece of tube w/ the valve and a hose clamp to seal it to the tank. I suppose that would work too, but then you have to have a clip on air chuck mine would not start at all wound up. Going to a car show instead local show and shine. Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558892 Share on other sites More sharing options...
mrsmackpaul Posted September 22 Share Posted September 22 Even if the system is dry, on a air start truck it will start in two tanks of air If a hand primer is fitted, just chuck the new filters on, pump the primer, you will feel it when it is primed and bypassing back to the tank Fill the air start tank and hit the giddy up and go switch and let the magic happen Paul Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-558904 Share on other sites More sharing options...
Old_DM Posted 2 hours ago Author Share Posted 2 hours ago My truck started loosing prime before I got to changing the filters. It had mysteriously died on me a couple of times, only to start again with 30-60 seconds of cranking. Finally gave it up after sitting for an hour shut down after a days use. Luckily I remembered this thread and cleaned up the hand primer, pumped it for a minute until there was noticeable resistance and the truck started right up. The hand primer leaked a bunch on the first few pumps but then sealed. Parts book doesn't show the lift pump / primer as having any internal parts available. Looks like PAI makes replacements for both the pump and primer. Anyone have experience with them? The parts book also shows no gasket between the lift pump and the injection pump housing. That can't possibly be right. Or do they expect you to slobber it with some sort of sealant? Quote Link to comment https://www.bigmacktrucks.com/topic/74548-endt-675-priming-after-fuel-filter-change/#findComment-561987 Share on other sites More sharing options...
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