Injector blowby LB7

J

Jdherron

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Aug 12, 2023
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Hey guys, I’ve got a problem that’s been totally stumping me. I just replaced my injectors (45 overs from DDP, used but unknown miles), injector cups, rebuilt my turbo (67mm kit from KB diesel) and did my head gaskets. After I put everything back together, it ran well for about thirty minutes and then started leaking oil, blowing by, and I had a ton of diesel in my oil. So I tore it down, saw that the o rings had blown out on a couple injectors, so I figured it was blowing by the coppers. I replaced all my coppers and o rings, cleaned the cups, and reseated the injectors. This time it ran perfectly for about 3 days before the same thing happened again. What could be causing the injectors to keep coming unseated?

My balance rates are all within spec
Compression test results:
Cylinder 8 - 380
Cylinder 7 - 365
Cylinder 6 - 360
Cylinder 5 - 350
Cylinder 4 - 365
Cylinder 3 - 370
Cylinder 2 - 390
Cylinder 1 - 350


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JoshH

JoshH

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Fuel in oil is usually either return lines leaking, injector lines leaking, or injector bodies leaking. A lifted injector doesn't usually get fuel in the oil.
 
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Bdsankey

Bdsankey

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Jdherron said:
Not sure about the hold downs, I’ll check tonight. All the discs are there, I double and triple checked


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Is it the same injectors coming unseated every time?


JoshH said:
Fuel in oil is usually either return lines leaking, injector lines leaking, or injector bodies leaking. A lifted injector doesn't usually get fuel in the oil.
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This has been my experience as well.


Jdherron said:
What’s the best way to test that?


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Vacuum test. AKA pull vacuum on each individual return line bank (IE the fitting coming from the head), that would verify the return side.
 
J

Jdherron

New member
Aug 12, 2023
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Tennessee
Bdsankey said:
Is it the same injectors coming unseated every time?



This has been my experience as well.



Vacuum test. AKA pull vacuum on each individual return line bank (IE the fitting coming from the head), that would verify the return side.
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Okay, I spent a few hours on it last night and have a few updates.

1. I did the vacuum test and the return lines were leaking like crazy, I found the leak by using a pump to pressurize the lines and used a little soapy water to find the leak. Turns out it wasn’t seating against injector 7. I pulled it off, cleaned the surfaces, new banjo washer, etc and it’s way better but won’t hold a perfect vacuum still. It’ll go down from 15 to 0 in 5 minutes or so. Any advice?

2. The hold down brackets looked good but I don’t really know what to look for on those, I ordered 8 new ones just to be safe

3. I read on another forum that an overfull crankcase can cause blowby. Could that be what’s causing my blowby more than an unseated injector, since there was so much diesel in the crankcase from the leaking return line?


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J

Jdherron

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Aug 12, 2023
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Tennessee
Hey y’all I posted another thread about some of the problems I’m having but I’m making a new one for this specific question. I did new injectors and after driving for a couple days it started blowing by and making oil. I found a leaking injector return line and discovered it’s just been pouring diesel into my crankcase. I read on another forum that an overfull crankcase can cause blowby, could that be what’s causing my blowby since there’s so much diesel in my crankcase?


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2004LB7

2004LB7

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How much torque on the return banjo bolts? I always put a few extra lbs then spec until I could feel the washer properly crush and seal. Maybe put another 1/4 turn on them and see if they seal up
 
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J

Jdherron

New member
Aug 12, 2023
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Tennessee
TheBac said:
No need for multiple threads on essentially the same topic. You're going to have to redo the injector job.
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Yeah that’s what I’m doing but I already redid it once and it didn’t fix it, so I’m trying to track down what keeps causing the problem. I’m redoing the injector job right now, I’m asking for help so it doesn’t happen again.


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J

Jdherron

New member
Aug 12, 2023
22
3
3
Tennessee
2004LB7 said:
How much torque on the return banjo bolts? I always put a few extra lbs then spec until I could feel the washer properly crush and seal. Maybe put another 1/4 turn on them and see if they seal up
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I torqued them a little past spec, the one that was leaking I torqued quite a bit further, about as far as I felt it could go without damaging the bolt or threads


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Bdsankey

Bdsankey

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Jdherron said:
I torqued them a little past spec, the one that was leaking I torqued quite a bit further, about as far as I felt it could go without damaging the bolt or threads


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What fastener are you using for return bolts?


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2004LB7

2004LB7

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Jdherron said:
I torqued them a little past spec, the one that was leaking I torqued quite a bit further, about as far as I felt it could go without damaging the bolt or threads


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Shouldn't have to go that tight. Infact, too tight can cause it to leak by damaging the washer. You only want to lightly crush the washer. Maybe there's a bur or rough spot on the sealing surface
 
J

Jdherron

New member
Aug 12, 2023
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3
Tennessee
Okay so I reinstalled everything again and once again I’m getting blowby. There was no blowby yesterday or this morning, but now there’s just enough to make the oil cap jump around. I replaced hold downs, coppers, and hold down bolts. Any ideas? I’m at a total loss.


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