Hey guys, I have an 01 Sierra with an LB7. Just did head studs, injectors, heads rebuilt, airdog 165. I rebuilt the motor and it ran perfect for about a week and now I have a bad knock and crazy balance rates. I understand that it could be a stuck injector but I'm not having any luck figuring out which one or if it is an injector at all! I have to get this thing figured out. It starts and idles fine other than the knock. With the injectors unplugged and turning the motor over everthing sounds nice and quiet. Check out these balance rates. I don't get it. I know you guys can help. AAAAAHHHHHHHH!

 

Here's what I've got goin on.

 

check out this link
How To: DIY - Injector cleaning - Chevy and GMC Duramax Diesel Forum

good info on cleaning injectors that may improve balance rates

those numbers just seem way out of whack. try the cleaning first. if that doesn't help then consider getting them checked with a Tech II to compare to your Edge before taring it back down to replace injectors

PS, balance rates are checked with engine fully warmed up. check in park/neutral and in drive. should have two sets of balance rates. which one is your test from?

 

are they stock injectors or aftermarket. are they brand new? how long have those injectors been ran?

 

They are brand new (not reman) II 20% over. They have only been in the truck for a week before this problem. I'm getting myself confused with injectors affecting cylinders other than the one with the bad balance rate.

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I've been swapping injectors around today and I'm not seeing anything different.

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Would valve problems cause any of these symptoms?

 

Alright, maybe this will help someone else that's having problems. I been having all of these "injector problems" that turn out to probably not be injectors at all. I decided to check my compression and found some interesting numbers.
1-320
2-350
3-360
4-0!
5-300
6-320
7-295
8-360

If you'll look at my second post you'll see injector #4 is going nuts. When I saw this big fat 0 my outlook looked pretty dim. I did rig up an air hose that would blow air into my glowplug hole all nice and sealed up. I have air coming out of the y-bridge(intercooler disconneted). I guess I'll pull the head and see what I see. Is there a chance the intake valves are screwed but the piston is ok? That would account for the leakage right? Just a side note, I have the rockers loosened so the valves should be sealing completely. Is cylinder #7 crapping out too? Please let me know what you guys think.

 

squirt some heavy weight oil into the cylinder, rotate the engine a little to get the rings coated. if the numbers improve then its likely that your cylinders/rings are shot.

air coming out of the y-bridge, that's got to be an open valve

at zero PSI makes one think you got a hole/crack in the piston, but then again you would probably shoot a dipstick if you did

 

With it being 0 i would say its most likely a badly burned or broken valve.

 

So it turns out crazy after all . One of the #4 cylinder intake valves dropped and now I need a new head and piston.