Gravelguy413 Posted March 19, 2021 Share Posted March 19, 2021 Have a 96 E7 all mechanical with Bosch pump. When the truck is running it runs and idles great. Turn it off and it will start the next day. Let it sit for a few days and it will not start without cranking the piss out of it. Do not see any obvious leaks in the fuel lines. Something is causing it to lose prime. Which parts should I replace first any ideas? What causes is to lose prime? Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/ Share on other sites More sharing options...
Popular Post OldRedMack Posted March 19, 2021 Popular Post Share Posted March 19, 2021 Check the filter housing for a Crack, took us 2 years to finally find that on 1 of our trucks. 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471065 Share on other sites More sharing options...
Popular Post Joey Mack Posted March 19, 2021 Popular Post Share Posted March 19, 2021 I beleive theres a check valve in the lift pump, and if yours has a hand primer, check it too.. the filter pads can crack just like O.R.M. said... One time I took a fuel filter off to find the threads on the stud were jacked up and the filter didnt seal right.. that one took me a while to find as well... Jojo 2 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471077 Share on other sites More sharing options...
theakerstwo Posted March 19, 2021 Share Posted March 19, 2021 Yes the lift pump has to hold the prime and on some pumps the check valve in the return port of the pump will hold the prime or help but like the CH i am running it has no check valve in the return but has a orfice fitting so go figure. Quote glenn akers Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471088 Share on other sites More sharing options...
Joey Mack Posted March 19, 2021 Share Posted March 19, 2021 🤔 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471089 Share on other sites More sharing options...
Gravelguy413 Posted March 20, 2021 Author Share Posted March 20, 2021 Ok I will check filter housings and put a new lift pump on it and see if that does it. Thank you for the replies. Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471112 Share on other sites More sharing options...
MACKS Posted March 20, 2021 Share Posted March 20, 2021 I am having the exact same problem on the exact same engine,I replaced two fuel lines so far,gonna do one more,if that doesn't work will swap out the lift pump.. Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471125 Share on other sites More sharing options...
fjh Posted March 20, 2021 Share Posted March 20, 2021 Check all the plastic return lines to the head and the little jumper between the head as well, also have your oil sampled for fuel the orings on the injectors can be an issue! just another place to look if all else fails! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471127 Share on other sites More sharing options...
MACKS Posted March 20, 2021 Share Posted March 20, 2021 5 hours ago, fjh said: Check all the plastic return lines to the head and the little jumper between the head as well, also have your oil sampled for fuel the orings on the injectors can be an issue! just another place to look if all else fails! Just found a leak on the return line that goes to the front of the head,cut it back and reattached,I'll know Monday morning if that was my problem.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471140 Share on other sites More sharing options...
terry Posted March 21, 2021 Share Posted March 21, 2021 On 3/20/2021 at 12:19 PM, MACKS said: Just found a leak on the return line that goes to the front of the head,cut it back and reattached,I'll know Monday morning if that was my problem.. That will let it lose it's prime. terry Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471219 Share on other sites More sharing options...
Popular Post mrsmackpaul Posted March 22, 2021 Popular Post Share Posted March 22, 2021 Funny reading this, some years ago on here I got shouted down and told I was a fool for suggesting that when a diesel looses prime when sitting it's the return side of things So some useless information from this dum bunny Get some old inner tube, a big hose clamp, a couple of air line fittings and some big flat washers Cut the tube big enough to cover the fuel cap Put a hole in the middle of the rubber, a flat washer each side held on with the air line fittings Put the rubber over the fuel cap hole and tighten down with the big hose clamp Put some pressure in it, maybe regulate to 15 - 30 psi, it wont go boom as your tank has a breather and the tube will pop off pretty easy Once you have this accomplished you can see the entire fuel system under pressure to check for leaks If you cant find any leaks I'm betting the tube on the return that goes to the bottom of the tank thats inside the tank has broken off or is cracked Remember Im a fool so try not laugh to hard Seeya Paul 1 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471228 Share on other sites More sharing options...
Joey Mack Posted March 22, 2021 Share Posted March 22, 2021 too funny Paul... Hell I know less and less everyday... Jojo 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471232 Share on other sites More sharing options...
MACKS Posted March 22, 2021 Share Posted March 22, 2021 Oh well my problem still exists,started hard again this morning. . Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471254 Share on other sites More sharing options...
Joey Mack Posted March 22, 2021 Share Posted March 22, 2021 So when you remove the fuel filters, the fuel is low in the filter? Have you looked at the fuel lines from the tank to see if fuel is bleeding through them? I assume you checked the lines from the filter pads to the lift pump? There should be 3 lines and a #12 line that comes from the tank.. jojo Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471255 Share on other sites More sharing options...
fjh Posted March 22, 2021 Share Posted March 22, 2021 (edited) 13 hours ago, mrsmackpaul said: Funny reading this, some years ago on here I got shouted down and told I was a fool for suggesting that when a diesel looses prime when sitting it's the return side of things So some useless information from this dum bunny Get some old inner tube, a big hose clamp, a couple of air line fittings and some big flat washers Cut the tube big enough to cover the fuel cap Put a hole in the middle of the rubber, a flat washer each side held on with the air line fittings Put the rubber over the fuel cap hole and tighten down with the big hose clamp Put some pressure in it, maybe regulate to 15 - 30 psi, it wont go boom as your tank has a breather and the tube will pop off pretty easy Once you have this accomplished you can see the entire fuel system under pressure to check for leaks If you cant find any leaks I'm betting the tube on the return that goes to the bottom of the tank thats inside the tank has broken off or is cracked Remember Im a fool so try not laugh to hard Seeya Paul This here Idea from the( bunny from down under )😂 makes some sense Its much easier to find a leak under pressure Than under vacuum! I have done the bunny trick also and if you have an external leak! you'll likely find it! It sounds to me its a leak behind the primer pump could be a check valve in the pump or secondary filter by the description of the time line! As others described crack in a filter head or filter can a bad line ect! Just my opinion Edited March 22, 2021 by fjh 2 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471258 Share on other sites More sharing options...
MACKS Posted March 22, 2021 Share Posted March 22, 2021 9 hours ago, Joey Mack said: So when you remove the fuel filters, the fuel is low in the filter? Have you looked at the fuel lines from the tank to see if fuel is bleeding through them? I assume you checked the lines from the filter pads to the lift pump? There should be 3 lines and a #12 line that comes from the tank.. jojo Thanks ,gonna check it all,I'll find it,I hope..lol Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471275 Share on other sites More sharing options...
Popular Post MACKS Posted March 23, 2021 Popular Post Share Posted March 23, 2021 So I ended up replacing that whole return line,it was so brittle couldn't get a tight fit,fired right up this morning... 3 1 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471309 Share on other sites More sharing options...
fjh Posted March 23, 2021 Share Posted March 23, 2021 Hope🤞fully it stays that way! 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471313 Share on other sites More sharing options...
Popular Post Gravelguy413 Posted April 3, 2021 Author Popular Post Share Posted April 3, 2021 Replaced both plastic return lines coming from front of head and also the smaller one that comes off the same fitting on back of injection pump. Problem solved 3 1 Quote Link to comment https://www.bigmacktrucks.com/topic/66302-hard-starting-e7/#findComment-471979 Share on other sites More sharing options...
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