Major LB7 problems -- need help

N2BRK

Well-known member
Dec 31, 2009
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I know you can't compress a liquid so I assume something would have to give up and get out of the way..

Unstoppable force meets uncompressible liquid... usually connecting rod gets shorter.

I've only done compression check through the glow plug hole. I don't see why you couldn''t go though the injector hole, but I'm not aware of an adapter that would let you do that.
 

Citidiot90

Person
Apr 22, 2020
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Unstoppable force meets uncompressible liquid... usually connecting rod gets shorter.

I think I'm ok as far as bottom end as the motor still runs lol

I've only done compression check through the glow plug hole. I don't see why you couldn''t go though the injector hole, but I'm not aware of an adapter that would let you do that.

I have an air cooled deutz engine that doesn't have glow plugs and basically you take a scrap injector and hollow it out and that becomes the adapter for the compression tester. Maybe a little more complicated of a setup than is needed for a Duramax. But I'm not a mechanic :thumb:
 

Bdsankey

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Feb 1, 2018
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Lol Its not bad advice. I don't have a compression tester unfortunately. Do you check compression through injector holes or glow plugs holes? I've heard of both methods depending on the tool. The tech who has my truck also told me that with faulty injectors I could lose compression through the injector itself. Waiting on a call back to see what he thinks I should do. Hes quite convinced it's more than one Injector hanging open. Said he heard the fuel knock as soon as I pulled up. I know you can't compress a liquid so I assume something would have to give up and get out of the way. Just hoping I can decipher that without pulling my head's or worse.

Unstoppable force meets uncompressible liquid... usually connecting rod gets shorter.

I've only done compression check through the glow plug hole. I don't see why you couldn''t go though the injector hole, but I'm not aware of an adapter that would let you do that.

^, do yourself a favor and check the compression. I've only ever seen kits/adapters for the glow plug location for a duramax. On tractors without glow plugs you have to get creative and make an adapter out of an old injector.
 

KyleC4

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Dec 30, 2016
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update when you get that one or bank of injectors done if it’s all fixed. You’re symptoms and repair may help someone else one day. :thumb:
 

torqued2dmax

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Mar 26, 2017
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Brookville, PA
The reason I suggested compression test last week post 32 is because it is not good for a rock to go through the intercooler and get eaten up by the turbo then chewed by the pistons for a while then spit out .
 

Citidiot90

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Apr 22, 2020
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update when you get that one or bank of injectors done if it’s all fixed. You’re symptoms and repair may help someone else one day. :thumb:

I certainly will keep this updated as I go. That's the beauty of this forum and It would make me so much happier to help others figure it out too :D

The reason I suggested compression test last week post 32 is because it is not good for a rock to go through the intercooler and get eaten up by the turbo then chewed by the pistons for a while then spit out .

I really hope that isn't the case :( although had it made it into the intercooler that would have been after the turbo anyway. I guess I'll find out the hard way. I'm thinking I might try to change out my grill for something more protective if I get this truck pulling again.

On a side note: I called the place I got the injectors from. They said I could ship them back and have them tested and they would cover manufacturer defects. Although I assume after waiting for months (if the courier doesn't lose the shipment) they would just point the finger at me and then I'd be out 8 cores. Wouldn't use them again. I would advise any newbies like me to be VERY CAREFUL choosing their parts supplier. I always assumed that parts were parts. Now I know better.
 

Cougar281

Well-known member
Sep 11, 2006
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St Louis, MO
The reason I suggested compression test last week post 32 is because it is not good for a rock to go through the intercooler and get eaten up by the turbo then chewed by the pistons for a while then spit out .
Except a rock entering the intercooler will never get to the turbo as the IC is post turbo... Making it into the engine is a different story.

Sent from my 2PZC5 using Tapatalk
 

torqued2dmax

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Mar 26, 2017
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Brookville, PA
Thanks for the reminder, it has been about 10 years since I had to do any plumbing to my eng and just remember the op saying about rebuilding turbo and the hole in the inter cooler
and thought it might have something to do with a compression loss if the rock fragments went into the eng .
 

torqued2dmax

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Mar 26, 2017
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Brookville, PA
Wait correct me if I am wrong , but after crap that gets into the eng from the inner cooler then exits the pistons through the exhaust valves then it dose go through the exhaust section of the turbo right ?
 

Citidiot90

Person
Apr 22, 2020
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Wait correct me if I am wrong , but after crap that gets into the eng from the inner cooler then exits the pistons through the exhaust valves then it dose go through the exhaust section of the turbo right ?

Woah . That blew my mind lol. Sorry no updates quite yet. Just finished limping truck home from mechanics... Tranny is acting up now too. Waiting for tomorrow so I can exchange some manifolds for some injectors
 

torqued2dmax

Member
Mar 26, 2017
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Brookville, PA
Just trying to suggest things that may help figure out your problem , it is never a good thing to have something go through your intercooler and get eaten by the eng and turbo , but I definitely hope that the injectors do the trick for you ! Good luck !
 

Citidiot90

Person
Apr 22, 2020
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Canada
So I pulled the passenger side injectors today. Number 3 +which was what the mechanic called) popped right out after I unbolted it. Is this suspect? Did I do something wrong installing? I also noticed the other injectors held some fuel in them in the high pressure port... But number 3 was dry. I'm assuming this idicates a problem. Any suggestions would be appreciated :)
 

Citidiot90

Person
Apr 22, 2020
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Canada
Problem solved. After replacing the passenger side injectors I've got smooth quiet idle and lots of boost. I'm still seeing some smoke at higher rpms but definitely feels like its running properly. Going to be doing the driver side next. I hope anyone who reads this and is having problems learns something from my ignorance.

It's very likely going to be an Injector issue.

On a side note, after paying $400 per injector, I didn't expect to see pitting on the high pressure port's sealing surface. I should have taken a picture. Hoping it doesn't cause problems but at this point I feel like swapping injectors is easy.