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Hard starting E7


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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?

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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.

glenn akers

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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..

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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!

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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..

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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:MackLogo:

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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

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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 by fjh
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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

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