LB7: Urgent help needed ASAP! Terrible thing happened after HG job!

blk smoke lb7

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Nov 8, 2010
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belvidere,ill
Alright well bad news but at least I know it's cylinder #4 which is the second one on the driver side. I had a solid 300psi everywhere and a very even ramp up. On cylinder #4 it was a very flat 80psi. Tested twice same result... Now I will be pulling the driver side apart to find out what happened. Oh! And no fuel was being dumped so I guess that means the injector is not stuck open. I hope I don't have a blown ring since I have no idea what that would all involve and I don't want to find out. I am very much hoping for a badly seated injector. If that is the case can I just seat it back down with new o-rings and copper washer? Should I reset the cup? Put a new cup?

Scott do you recall the compression on that one cylinder? Was it that low?
Yes it was 200 but his barely knocked im guessing yours may be a little looser.Josh drove the truck for a wek before his even started doing that.Yours from start up im guessing it might have been hand tight or a bit looser posibly.
 

fishv12

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Jan 30, 2011
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Thanks for all your help guys! I truly appreciate it. I will start parting my truck out this afternoon. I don't quite know how long it's going to take me but considering that I have done that job once already I think I will be a little faster this time around. Also none of the fasteners should give me a problem.
 

gmac32

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Dec 8, 2009
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i had a customers truck that had a similar problem. If you let his sit a couple days, it added enough antifreeze in that cylinder that when you started it, it would hydrolock and bent the rod. The knock came from the piston skirt hitting the crank. hopefully you don't run into a situation like that
 

fishv12

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Jan 30, 2011
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Well if I had coolant into the cylinder I think I would of seen it when I did the compression check. No liquid came out of the glow plug hole while cranking everything was dry including the glow plug tips. I parted out most of the driver side but since I lent my fuel line disconnect tool I didn't have it and I came to a dead stop. I will be picking that up today and hopefully have the covers off by this evening.

Like I said I am very much hoping for a badly seated injector. But I have a few questions... If that is the case can I just seat it back down with new o-rings and copper washer? Should I reset the cup? Put a new cup?
 

blk smoke lb7

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Nov 8, 2010
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belvidere,ill
As much set up time as you gave it i would think you would be fine,also i would think you would have some coolant leaking into the cylinder.
 

fishv12

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Jan 30, 2011
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Scott: How do you figure there is coolant leaking in the cyl? Just don't quite understand what you just said.
 

adeso

wait, what?
May 30, 2011
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Minot, ND
I would pull the valve covers off and check that injector like the guys said. at 40PSI is should be clear what the problem is. I'm guessing with no coolant in there that it is an injector not seated.
 

blk smoke lb7

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Nov 8, 2010
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belvidere,ill
Sorry I was in a hurry getting ready for work and didnt proff read that.I was saying I think you will be fine as the glow plug had no coolant on it and you gave it a long time set up time for the loctite so I would think you should be fine on the cup staying sealed.
 

fishv12

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Jan 30, 2011
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Well here is the deal. I had an injector that was loose as Scott guessed it :). Not because I didn't tight the fastener to the required torque though. The only reason I can think of is a broken thread on the bolt which also damaged the threads within the head. I took my time and tapped and cleaned the threads within the head but I can tell that there was some damage done and the fastener was a little loose inside. Now I am not sure what I should do but I was thinking of using some kind of loctite which should ensure it's held in place. What kind of loctite would you guys recommend? I would like something that would break free if I need to change the injector at some point and obviously it needs to be resistant to heat.

I would also need some help with part numbers as I will be calling tomorrow my local GM dealer. I need a new injector copper crush washer, injector o-ring and injector hold down bolt.

Thanks for the help guys I am really relieved to find it was the injector!
 

blk smoke lb7

<-----Lots of green $
Nov 8, 2010
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belvidere,ill
Well here is the deal. I had an injector that was loose as Scott guessed it :). Not because I didn't tight the fastener to the required torque though. The only reason I can think of is a broken thread on the bolt which also damaged the threads within the head. I took my time and tapped and cleaned the threads within the head but I can tell that there was some damage done and the fastener was a little loose inside. Now I am not sure what I should do but I was thinking of using some kind of loctite which should ensure it's held in place. What kind of loctite would you guys recommend? I would like something that would break free if I need to change the injector at some point and obviously it needs to be resistant to heat.

I would also need some help with part numbers as I will be calling tomorrow my local GM dealer. I need a new injector copper crush washer, injector o-ring and injector hold down bolt.

Thanks for the help guys I am really relieved to find it was the injector!
I can send you an injector hold down bolt but if the dealer has 1 instock probably worth getting it from them as if i send it out(i would just send you 1 no problem) it wont get there for a few days im guessing.Not sure how much of a hurry you are in,i think i have them from 10 differant engines so im sure i could spare it.:D
 

slipclutchms

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May 24, 2010
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Green locktite. It is called bearing it sleeve retaining compound and it expands like 5 or 8 thou. Those bolts won't come out again :)
 

blk smoke lb7

<-----Lots of green $
Nov 8, 2010
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belvidere,ill
I have never used it but they have that aluminum form a thread.Guess i would try that 1st.Is it striped or week in the hole? could try red high temp loctite if it will stay firm in the hole.
 

fishv12

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Jan 30, 2011
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Well I do have lots of the red 272 loctite I purchased to put the cups in but I am a little worried since I do want that bolt to come out if ever I do injectors. It seemed loose inside for the first half but the bottom threads seemed fine.

Scott many thanks for the offer on the bolt but I am hoping to get this quick. If I could find a GM part number that would be great.
 

fishv12

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Jan 30, 2011
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There is a product called loctite form a thread maybe something to look into... It's good up to 300F which I think would be sufficient for the hold down... I would use an helicoil but considering it's not even that bad I just don't think it's the best thing to use in my case.
 

fishv12

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Jan 30, 2011
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I must be tired I re-read your response Scott and you had mentioned the form a thread stuff. Time for me to go to bed! The bolt seems to stay firm for the last bit anyways... With the new bolt in it will go even deeper and hit those good threads some more as I cut the bad part of the original one out to check so it's a little on the short side. I probably would be fine with the red loctite but I will take a look for the form a thread stuff. I think that would be even better in my case... Unless someone says otherwise.
 

fishv12

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Jan 30, 2011
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I found the following numbers for the parts:
Copper inj. crush washer 97216082
Bolt 97221511
Oring 94011699
 

fishv12

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Jan 30, 2011
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Yesterday morning I ran over to two different dealerships to find my bolt, oring and copper crush washer. I then found the loctite repair thread compound and gave it a shot. I didn't have any luck with it. My hole was clean and bone dry. And my new bolt very very clean and soaked in release agent just like the instructions states. I waited a full 10 minutes to pull out the bolt when the instructions called for 5-10 and the bolt came out with set glue all over it. The hole didn't look at all different. I guess I could of gave it a second go and tried it again but I just got fed up. I tapped the hole again to make sure it was clean then cleaned everything with brake cleaner and used loctite 272 on the bolt threads and re-installed everything. I guess if ever I need to take that sucker out I will need to put a little heat with a small flame torch of some kind. I may also have to consider fixing the threads with an helicoil kit which is the only thing I can think of.

Valve covers are back on and fuel lines are in I just need to button up the rest and I am a go!
 

fishv12

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Jan 30, 2011
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Oh for future reference for myself and others the bolt size is M10X1.5 for the injector hold down. One more thing I could do is try to find a slightly bigger bolt but that's not that easy to do.