Injector balance rate question - Chevy and GMC Duramax Diesel Forum
04.5-05 LLY Duramax Powertrain Discussion of components that are directly involved in the power production and all that is needed to get and keep the truck moving . Engine , Transmission, Etc.

 
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post #1 of 10 (permalink) Old 07-21-2019, 04:24 PM Thread Starter
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Injector balance rate question

Started looking at my injector balance rates cause I'm hearing what sounds like injector knock around 1800-1900 rpm underload. Don't really hear it at idle.

Tested at operating temp at idle
Injector #1 -0.7 #2 1.1 #3 -0.3 #4 4.2 #5 1.3 #6 -1.3 #7 -3.2 #8 -1.1

So #4 looks questionable and so does #7

But my question was something I read about corrected values mentioned something that LLYS and "9mm3" but I'm not understanding what they were talking about.

Can anyone shed some light on this?
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post #2 of 10 (permalink) Old 07-21-2019, 04:36 PM Thread Starter
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The more I'm reading it seems like it might be a good idea to just replace my injectors with new ones because if I replace one or two the other injectors will have to compensate in order to keep up? Idk the truck has 150k on it and wouldn't be surprised if it's just time to replace them as a maintenance thing. I just installed a brand new CP3 do to it failing so I can imagine the injectors are probably pretty tired.
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post #3 of 10 (permalink) Old 07-21-2019, 05:40 PM
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Look up the diy injector cleaner that's NOT ran through the fuel tank. It is discontinued I believe but can be found. Try that or dump a full bottle of additive in. Check the injector harness behind the alternator for rubbing and might as well ice pic them at the same time as it is usually 4 n 7 that have issues. Your rates arent that bad to go replacing injectors just yet. Also your fuel knock around that rpm could possibly be the pilot injection turning off also.
The mm3 thing your talking about is how much fuel is being injected. The older fixed vane trucks ran around 7 to 8 mm3 at idle the lly+ were a little higher because of something to do with the engine idling higher and the vvt turbo needing more fuel at idle, I cant remember. But yes they idle around 9 to 11mm3. Theres a good thread on diesel place(before it went to shit) about balance rates I'll try to find it.

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post #4 of 10 (permalink) Old 07-21-2019, 07:05 PM
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The 9mm^3 flow rate is the average expected to feed the whole common rail. You also need to measure the actual to get the difference, which then gets added or subtracted to each cylinder balance rate. So unless you can measure the main pump flow rate do not worry about this number.

150k for LLY and newer engines is nothing. Most go 200k+ before replacing any injectors, but it's not impossible you need to replace one or two. Also, you don't measure these rates just once. Every time you run the vehicle the rates will change. Only when the rates consistently stay outside the spec range or are wildly out does it indicate a problem.

Replacing one injector at a time is typical on LLY and newer engines. One injector should not cause other cylinders to compensate, each injector acts on its respective cylinder. If replacing one injector does cause other rates to change, it's because the main flow rate changed along with the new injector, and the other injector readings are simply adjusted to the new flow rate since they are average offsets from the main flow rate.

2005 LLY 3500 CCLB 215,000 miles
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post #5 of 10 (permalink) Old 07-21-2019, 07:20 PM
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My name is Nic
2011 GMC Sierra 2500 CCSB LML,
Lil ole single s400, fuel,
supporting mods,
rancher tuned,
Various parts from SDP, WCFAB, LDS, DHD,
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post #6 of 10 (permalink) Old 07-21-2019, 08:03 PM Thread Starter
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Quote:
Originally Posted by SilverGorillaLML View Post
Look up the diy injector cleaner that's NOT ran through the fuel tank. It is discontinued I believe but can be found. Try that or dump a full bottle of additive in. Check the injector harness behind the alternator for rubbing and might as well ice pic them at the same time as it is usually 4 n 7 that have issues. Your rates arent that bad to go replacing injectors just yet. Also your fuel knock around that rpm could possibly be the pilot injection turning off also.
The mm3 thing your talking about is how much fuel is being injected. The older fixed vane trucks ran around 7 to 8 mm3 at idle the lly+ were a little higher because of something to do with the engine idling higher and the vvt turbo needing more fuel at idle, I cant remember. But yes they idle around 9 to 11mm3. Theres a good thread on diesel place(before it went to shit) about balance rates I'll try to find it.
I ice picked injector 7 already and can't remember if it was 2 or 4 that I ice picked as well. And Im running injector cleaner through it now.
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post #7 of 10 (permalink) Old 07-21-2019, 08:05 PM Thread Starter
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Originally Posted by Shibby6600 View Post
The 9mm^3 flow rate is the average expected to feed the whole common rail. You also need to measure the actual to get the difference, which then gets added or subtracted to each cylinder balance rate. So unless you can measure the main pump flow rate do not worry about this number.

150k for LLY and newer engines is nothing. Most go 200k+ before replacing any injectors, but it's not impossible you need to replace one or two. Also, you don't measure these rates just once. Every time you run the vehicle the rates will change. Only when the rates consistently stay outside the spec range or are wildly out does it indicate a problem.

Replacing one injector at a time is typical on LLY and newer engines. One injector should not cause other cylinders to compensate, each injector acts on its respective cylinder. If replacing one injector does cause other rates to change, it's because the main flow rate changed along with the new injector, and the other injector readings are simply adjusted to the new flow rate since they are average offsets from the main flow rate.
So would it be worth while to just do injector #4 and #7 everything else should be good I just replaced the CP3 cause it was surging really bad also did a FASS lift pump at the same time
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post #8 of 10 (permalink) Old 07-21-2019, 09:08 PM
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Quote:
Originally Posted by Tom Williams View Post
Started looking at my injector balance rates cause I'm hearing what sounds like injector knock around 1800-1900 rpm underload. Don't really hear it at idle.

Tested at operating temp at idle
Injector #1 -0.7 #2 1.1 #3 -0.3 #4 4.2 #5 1.3 #6 -1.3 #7 -3.2 #8 -1.1

So #4 looks questionable and so does #7

But my question was something I read about corrected values mentioned something that LLYS and "9mm3" but I'm not understanding what they were talking about.

Can anyone shed some light on this?
Your injectors really are not that far out of spec, also every time you check the rates the numbers will be a little different. The one thatís a little high now, will be better and another one will take its place.

Iíd try using a good diesel additive and run some thru every tank from here on out, and check your rates more often.
Donít jump to conclusions until you try diesel additives with lubricant.
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post #9 of 10 (permalink) Old 07-21-2019, 09:17 PM
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I wouldnt replace those injectors yet. They arent bad yet. If they get worse over time then I'd swap them out. Check out Lincoln diesel specialists for injectors when it is time

My name is Nic
2011 GMC Sierra 2500 CCSB LML,
Lil ole single s400, fuel,
supporting mods,
rancher tuned,
Various parts from SDP, WCFAB, LDS, DHD,
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post #10 of 10 (permalink) Old 07-21-2019, 10:38 PM Thread Starter
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Quote:
Originally Posted by D_R_C View Post
Quote:
Originally Posted by Tom Williams View Post
Started looking at my injector balance rates cause I'm hearing what sounds like injector knock around 1800-1900 rpm underload. Don't really hear it at idle.

Tested at operating temp at idle
Injector #1 -0.7 #2 1.1 #3 -0.3 #4 4.2 #5 1.3 #6 -1.3 #7 -3.2 #8 -1.1

So #4 looks questionable and so does #7

But my question was something I read about corrected values mentioned something that LLYS and "9mm3" but I'm not understanding what they were talking about.

Can anyone shed some light on this?
Your injectors really are not that far out of spec, also every time you check the rates the numbers will be a little different. The one that’s a little high now, will be better and another one will take its place.

I’d try using a good diesel additive and run some thru every tank from here on out, and check your rates more often.
Don’t jump to conclusions until you try diesel additives with lubricant.
Quote:
Originally Posted by SilverGorillaLML View Post
I wouldnt replace those injectors yet. They arent bad yet. If they get worse over time then I'd swap them out. Check out Lincoln diesel specialists for injectors when it is time
I'm running Stanadyne fuel injector cleaner right now just hearing that knock is disconcerning
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