• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

05 LLY injector knock PLEASE HELP

Nick 6.5

Active Member
Messages
197
Likes
81
Location
California
Thread starter #1
4ED73B50-6471-42E6-BA06-BEF2CA8BF38D.jpeg This has been a covered issue but can’t find the exact issue been having. I️ have an 05 lly that has been getting a knock. It honestly sounds to me like rod knock though I’ve heard that’s rare on duramaxs. I️ know for sure it’s not a broken crank. The part that makes me think it’s a rod is is I️ can hear this knock at idle where most people I’ve read only hear injector knock at higher rpm. My balance rates are out of wack a bit but can this cause it to knock like that through the rpm range? Don’t have any back smoke or haze at idle or under acceleration(another reason thinking rod). Hoping to god I don’t have to do a bottom end. I️ have checked the clips at the injectors and all look good. Also checked the rub spot by the alternator bravket and didn’t see any issues. I’ve ran a small bottle of hotshot diesel extreme in the tank trying to get the injector rates under control and did a hot soak with sea foam but didn’t get much change. The pic is my current balance rates after the hot soak with new fuel Filter and the injector cleaner in the tank. The truck is 100% stock mechanicaly. I️ just got the truck about 2 weeks ago. It ran fine with no knock at all. The knock is a new development within that last couple days. It was a theft recovery so I️ don’t know any history on the truck. Anyone have any input or advice to try? I’m all ears.
 

MrMarty51

Well-Known Member
Messages
1,324
Likes
1,241
Location
Miles City, Montana
#2
If the injectors are electronically fired, Unplug one injector at a time with the engine running and plug them back in, when You get to the knocking cylinder, if it is a rod, the knock will stop. If it is not the cylinder that is out of balance then You will know it is a rod.
I do not know a thing about these engines, and I do not know if unplugging one injector at a time will harm any components, besides possibly setting a code.
The test could also be done with shutting the engine down when unplugging, plugging injectors back in.
Maybe @THEFERMANATOR will come in and give You better information.
 

Nick 6.5

Active Member
Messages
197
Likes
81
Location
California
Thread starter #3
Thanks you Marty for the reply!! Believe got it figured out. Did some trouble shooting and it seems there is a short somewhere in my harness. I️ switched #8 injector with #3. Trying to trouble shoot the injectors. And checked my balance rates again. Now it’s showing #4 is high. Didn’t touch 4 tho. So pretty sure it’s in my harness somewhere
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
9,069
Likes
2,485
Location
ZEPHYRHILLS FL
Staff #5
Ok, 1st things 1st. No, you cannot unplug the injectors 1 at a time to find the miss. Lly's are 48 volt injectors, they're fired via a FICM that turns 12 volts into 48 volts to open the injector, the FICM controls the injectors in 2 groups of 4, if even 1 injector in a group goes out, the FICM shuts the whole group down, and you now have a 4 cylinder.

2nd, LLY's are unique in that the ONLY RELIABLE scanner is a TECH 2. ANY other scanner(yes, even an EFILIVE V2 or autocal) can read injector/balance rate info incorrectly as well as shut off the wrong commanded injector. So theres a good chance the balance rate DID follow that injector.

3rd, you MUST have a TECH 2 if you want accurate data for an LLY, it's just how they are.

I highly doubt you have a rod knock that you can hear over the diesel noise that you wouldn't hear ALL the time. Also, I would do some reading. Balance rates without the fuel rate are just numbers.

http://www.thetruckstop.us/forum/threads/proper-way-to-check-balance-rates.41579/
 

Nick 6.5

Active Member
Messages
197
Likes
81
Location
California
Thread starter #6
Thank you ferm. I️ figured that unplugging the injectors wouldn’t work. Did an oil change and I have no sparkles in the oil or on the filter element inside the filter so figured is not rod knock. The knock I could hear at all rpm including at idle. I️ did not know about the tech 2 scanner thank you for that.
 

THEFERMANATOR

FRANKENBURBAN
Staff member
Lead Moderator
Messages
9,069
Likes
2,485
Location
ZEPHYRHILLS FL
Staff #7
Thank you ferm. I️ figured that unplugging the injectors wouldn’t work. Did an oil change and I have no sparkles in the oil or on the filter element inside the filter so figured is not rod knock. The knock I could hear at all rpm including at idle. I️ did not know about the tech 2 scanner thank you for that.
Many a person has chased injector problems on LLY'S using there EFILIVE V2 only to learn about only the TECH 2 displaying the correct data streams. GM even went so far as to scramble a couple of the data streams on the LLY so that they change at a certain RPM point. They found the injector disable command would shutoff 1 injector at idle, but as soon as you touched the throttle it would switch to another. Welcome to LLY life and why so many DESPISE them. If you think this is bad, try flashing them. It's like russian roulette everytime you click start flash if it will go through or brick on you.
 

Nick 6.5

Active Member
Messages
197
Likes
81
Location
California
Thread starter #8
DO you generally hear the injector knock at idle?? I can hear a definitive knock under the truck and beside it at idle as well as all the way up through the rpms
 

Nick 6.5

Active Member
Messages
197
Likes
81
Location
California
Thread starter #10
Ok. I had read that you generally won’t hear injector knock at idle. Thank you for that info! This is why I love this forum! Real knowledge from people who know their shit!! Thank you again sir!
 

WarWagon

Well it hits on 7 of 8...
Messages
8,313
Likes
2,799
Location
AZ
#11
You sure you don't want to step back and ask "I have an engine knock?" I have no context as to how loud it is.

Check the vibration damper, TC bolts, drop and check the fan belt, check all the fan belt drive accessory bearings. Check engine mounts. Check exhaust for hitting somewhere: aftermarket exhaust?

Good call to cut open the oil filter. A oil sample would be interesting, but, neither told me squat before I rebuilt then replaced a Cumapart.

How the trans oil look? The converter is spinning with the engine so don't rule it out.

As far as the harness: The connectors at the injectors are famous for problems. Google How To: Ice Pick Injector Harness/ Connectors.
 

Nick 6.5

Active Member
Messages
197
Likes
81
Location
California
Thread starter #12
71E382CF-9155-4D91-A559-A867CEE52EAF.jpeg War wagon thanks for the reply!i haven’t been on in awhile. So my buddy owns a shop and he didn’t a quick scan with his tech 2. He didn’t have much time to actually look at it. And I read the ferms posts about balance rates and honestly it confused the shit out of me. I need to read it again when I have more time. I did replace #1 injector already and still knocks. So basically I did everything you just said before hand before I read this message. But, the knock is still there. Oil filter was clean no silver in the filter that was noticeable on the element and very very little residue on the filter mag. I did check the converter bolts and they were good. I’m not ruling out possibly a cracked flex plate but I’m leaning away from it cause the noise is from up front. I do have a bad driver side engine mount I’m most likely going to replace today. Have the parts already. Just had the trans serviced fluid was very dirty/grayish but not burnt. Probably going to need a trans soon :/ exhaust is 100% percent factorynand double checked not hitting anywhere. I did check the accessories thinking maybe water pump but the bearings felt smooth. The alternator is a little rough but the knock is coming from lower. There is a definitive knock at idle up through the rpm and then the turbo covers the sound of the knock. It seems to be coming from cyl #1 or #3. I was reading up on a possible cracked piston cause I do have some vapor coming from the fill cap but not an extreme amount. I know the engine produces windage so I’m taking that into consideration. It’s not enough to feel a puff or pressure against my palm. But I don’t have the symptoms of a cracked piston. Not a big enough crack that would cause that knock and certainly. Also I have No smoke no miss no check engine light. Runs just like normal perfect. Just and a personally irritating knock. And I have already done the ice pick for the connectors. I’m going to do a compression test Wednesday I think I should have time then. But I’m just stumped. I’m thinking I may have to take it into a shop :/ I keep trying to post videos of the knock and vapor but the site never lets me.
 
Top