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Discussion Starter #22 (Edited)
Ferm, excellent write up, but I have to ask....why are you stating that you are ADDING the fuel rate value to the balance rate, but your examples show you are SUBTRACTING it?
Which is it?
If your fuel rate is less than 8Mm3 of fuel, then you need to add the difference to the numbers. So if your balance rate is already a negative(meaning it is injecting less fuel than the indicated fuel rate), when you add the difference the number will be an even higher negative number as it will now be even furthur away from what the fuel rate should be. If it's a positive number, then you have to subtract essentially since your adding a negative amount. I'm not the best at doing write-ups, so thats why I did the examples. I just looked at them and it looks like I got them right, just got some of my description of the process is confuzling since I'm no tech writer.

When I did the write up at TTS I first posted it trying to get feedback on how clear my directions were BEFORE I posted it elsewhere(that plan got changed, so here it is).
 

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Using HPTuners Scanner there is a Main Fuel and a Total Fuel. These two values read about 1mm3 different all the time. I am assuming that the Total fuel includes the pilot injection as well as the main injection and the main fuel is just for the main injection. Is this right? Which one do I need to use?
 

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Below are screen shots of the HPTuners scanner set up for balance rates. First in Park, second in drive. I couldn't get the balance rates to show anything but 0 in Park unless I held the brake in. I didn't have this problem with the tune in it. This only happens with the stock tune.


Tell me what you think.
 

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Discussion Starter #26
If the balance rates go to far out of range, or if the fuel rate drops to low, the ECM will zero out the balance rates and sho 0 with the engine shaking. Is this whats happening?
 

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If the balance rates go to far out of range, or if the fuel rate drops to low, the ECM will zero out the balance rates and sho 0 with the engine shaking. Is this whats happening?
Kind of. The main fuel was low and every once and a while it would come up far enough for the balance rates to start showing. I wouldn't say the truck shakes. Sometimes it will get a lope sound to the idle. This is with the tune in it though and the balance rate read fine in park with the tune. Its when I put the stock tune in (I disables the EGR in the stock tune because mine is deleted) so almost stock tune, that the balance rates in park read 0 until I push the brake (which puts a small load on the motor).

Now here is whats strange. The truck runs great and the only time there is a little smoke is when you first punch it. or a little bit if you rev it up.
 

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No opinion on the balance rates I posted?
 

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Discussion Starter #29
The fuel rate of 2.5 in your first pic means you have to add 5.5 to all of your balance rates. When it dips below about 2 it will go blank on the balance rates, so the ECM is doing it's job. You have ALL of the signs of bad inejctors. I bet if you ramp up the fuel pressure at idle it goes to shaking and making all kinds of funny racket from to much feul returning through the inejctors. From what I can see from your screen shots, the only injector you have that is good is number 1(and even it is starting to push it). The rest are all well out of spec. You could try cleaning them with the GM upper engine cleaner and a gallon of diesel run through it, but as far out as they are I doubt it will do much.
 

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The fuel rate of 2.5 in your first pic means you have to add 5.5 to all of your balance rates. When it dips below about 2 it will go blank on the balance rates, so the ECM is doing it's job. You have ALL of the signs of bad inejctors. I bet if you ramp up the fuel pressure at idle it goes to shaking and making all kinds of funny racket from to much feul returning through the inejctors. From what I can see from your screen shots, the only injector you have that is good is number 1(and even it is starting to push it). The rest are all well out of spec. You could try cleaning them with the GM upper engine cleaner and a gallon of diesel run through it, but as far out as they are I doubt it will do much.


I kind of figured this would be your answer. I think there is a flaw either in this method of checking balance rates or with using the HPTuners scanner with this method. Reason being, using your method all but one of my injectors is bad, all except #1. Well....I just had to replace a head because it was cracked (leaking coolant externally). While I had the heads off and was cleaning the block I noticed the #1 cylinder had much more soot build up than the rest (a significant amount more). If I read the numbers displayed by the HPTuners scanner the balance rates match what I found upon the disassembly. Using your method says that is the only good injector.

This is where I am getting confused. I am not saying your way is wrong but maybe the HPTuners software already takes into account the fuel? I will get on the HPTuners forum and ask this question. In the meantime what are your thoughts?

If all of the injectors were bad wouldn’t the truck be running horribly? The idle will lope a bit from time to time (not all the time) and there is very little smoke. I would think if they were all bad it would idle horrible and would be smoking a lot.

BTW...I already bought the GM cleaner and am going to run it through either tonight or in the morning. Before I run it through I will hook up my auto engenuity and see if I can bump the pressure up manually.

EDIT: Also, why are you using the main fuel instead of the total fuel?
 

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Discussion Starter #31
The main fuel is the one normally displayed on most scanners. Your pilot shot is only about 1-1.5Mm3 of fuel. And the extra soot is a good sign. A clean piston top is normally a sign of leaking injectors, and the fuel cleaning the piston top. When I did my head gaskets my bad injectors were the ones with clean piston tops.
 

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So you're telling me a dirty cylinder is a good running cylinder? There is nothing that sounds right about that.

In my opinion this way of checking balance rates is extremely faulty. You claim I have 7 bad injectors yet my truck idles well, drives smooth, no surge, no smoke.........yet seven injectors are bad? Please explain that one.

Do you happen to sell injectors for a living?

Another issue is balance rates are not a reliable test for injector health anyways. A fuel return rate test is the proper way to do it. Lower compression in a cylinder can cause the balance rates to change and the change would have nothing to do with the injector.

Mods I would take a second look at having this as a sticky. This could lead people to replace a lot of injectors that do not need replaced.
 
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Discussion Starter #33 (Edited)
So you're telling me a dirty cylinder is a good running cylinder? There is nothing that sounds right about that.

In my opinion this way of checking balance rates is extremely faulty. You claim I have 7 bad injectors yet my truck idles well, drives smooth, no surge, no smoke.........yet seven injectors are bad? Please explain that one.

Do you happen to sell injectors for a living?

Another issue is balance rates are not a reliable test for injector health anyways. A fuel return rate test is the proper way to do it. Lower compression in a cylinder can cause the balance rates to change and the change would have nothing to do with the injector.

Mods I would take a second look at having this as a sticky. This could lead people to replace a lot of injectors that do not need replaced.
No I don't sell injectors, and I don't even work in a shop(at least not anymore). Just somebody who was trying to put info out there to help others. I have learned this info the HARD way from helping people who HAD been to shops that sell injectors, and couldn't get there trucks fixxed because at face value the balance rates all looked good. I know this info works for using EFILIVE, TECH 2, and SNAP ON scanners, have never used HP TUNERS data for it. Use the info at your own risk as it is nothing more than a "DIAGNOSTIC TOOL"! To many feel that a computer is the answer, when there is NO replacement for diagnostics. It is simply data your collecting to determine the problem.

And yes, soot on the piston top is a GOOD thing. A washed down clean piston top is a DIRECT indicator of an overfueling condition washing the soot off. Here's today's lesson of the day with pictures.
GOOD looking piston top.

Notice the nice uniform soot layer with easy to make out signs of the nozzle spray pattern. This what you WANT to see.
BAD looking piston top.

Notice the clean area, this was with a BAD injector in my OWN engine when I did head gaskets. This was with an injector that was still in spec when checking balance rates at face value WITHOUT accounting for the fuel rate offset. It showed a -2.45 but corrected was around a -3.5. Still in spec, but the clean area shows it was leaking fuel.
 

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Ferm, there could certainly be some promising technique in there but typically the proper way to diagnose injectors is to check them with balance rates then to do a return rate test to verify an actual leaking injector. Have you done this at all and would you please post the actual balance rates in park/drive, corrected method and the return test results? Also how does this method take into account differences in the compression ratios?

Not trying to be devil's advocate but I think it's important to note these items before people go out and spend their hard earned money.
 

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Discussion Starter #35
Ferm, there could certainly be some promising technique in there but typically the proper way to diagnose injectors is to check them with balance rates then to do a return rate test to verify an actual leaking injector. Have you done this at all and would you please post the actual balance rates in park/drive, corrected method and the return test results? Also how does this method take into account differences in the compression ratios?

Not trying to be devil's advocate but I think it's important to note these items before people go out and spend their hard earned money.
I've only tried one truck with lower compression ratio, and it worked fine on it. Yes I know about the difference between return and balance rates, but when you do corrected balance rates, I have found it conicides with the return rates and helps to check your inejctors without having to do a return rate test. To many times peopel automatically assume there balance rates are good, when in fact multiple injectors can go south and skew the numbers. That is why I did this write up was to help others have the tools to know what they should be seeing when they check these numbers. I've had multiple trucks come to me that dealers have said were fine, and needed CP3's. Check the balance rates using this method and find multiple failing injectors. Do a return rate test and the results back up the corrected balance rates.
 

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Proper way to check balance rates.... applies to all 2001-2010 DURAMAX's, LML's are as of yet unknown to this testing.

It drives me nuts to hear people say there balance rates are good, so how can they have bad injectors? Well they might THINK there balance rates are good, but in reality they can be quite the opposite. Balance rates are nothing more than how far off of the average fuel flow each injector is. All DURAMAX engines at idle will adjust the injection amount of fuel to each injector to allow the engine to run as smoothly as possible(until the inejction amount drops down below roughly 2MM3 of fuel, then the ECm freaks out and and goes to all 0's for the balance rates). It uses input from the crankshaft and camshaft position sensors to achieve this cylinder balance, and the amount of fuel plus or minus from the average fuel flow is the balance rate for each cylinder. Balance rate numbers can vary from -7 to +15.

To get the actual balance rate of your cylinders, you must know the fuel rate/injection amount at the time the balance rates are taken(this will become VERY clear in a few minutes why you MUST know this number). The engine should be at 170 degrees or hotter, at a normal 680 idle(01 idle at 600, and LMM's idle at 720), rail pressure should be 35MPA for federal LB7's, and 30 MPA for most others, the battery should be charged with no abnormal loads on the engine(IE A/C off), and vehicle speed is 0MPH(the ECm only does balance rates when the engine is idling, and vehicle speed is less than 2 MPH). The fuel rate/injection amount should be at 8-9MM3 of fuel with all of these conditions met(at sea level it is safe to use the 8MM3 of fuel number, at 5000+ feet use the 9MM3 of fuel number. VVT trucks(LLY+) with the turbo closed at idle like in stock tuning will be closer to 9-almost 10MM3 of fuel at idle due to the extra engine load to spin up the turbo at an idle with the veins closed. And your in gear under these conditions should be roughly 10-13MM3 of fuel. Here is where knowing the fuel rate is so important and why it MUST be figured in.

Let's use a hypothetical example here to determine actual balance rates VS the displayed balance rates. All above conditions are met, and here is the balance rates in neutral(I will skip the in gear as it is the same, just with a different +/- spec).

#1 -2.1
#2 1.4
#3 -0.8
#4 1.2
#5 -1.4
#6 -1.2
#7 2.1
#8 0.8

Well these numbers at first glance look great and well within the GM specs of +/- 4 in nuetral and +/- 6 in gear(ideal would be 0, but no 2 cylinders are idnetical so don't expect to see all 0's. If you you most likely have a serious problem and the ECM has reverted to fail safe and not doing balance rates), but lets correct them to ACTUAL. The fuel rate should be at least 8MM3 of fuel, but the fuel rate is 3MM3 of fuel for this example. So we need to add 5 to all of these balance rates to get the actual numbers. So lets see the corrected numbers.

So we are adding 5 because the fuel rate is 5 low? what if my fuel rate is 8 does that mean that this does not apply to me?

Am i missing something here?? your math has blatant disregard for +\- its all over the place.. here is how it would look if we all assume 5 is a positive number.


#1 -7.1 BAD -2.1 + 5 = 2.9
#2 -3.6 borderline 1.4 + 5 = 6.4 bad
#3 -5.8 BAD -.08 + 5 = 4.2 bad
#4 -3.8 borderline 1.2 + 5 = 6.2 bad
#5 -6.4 BAD -1.4 + 5 = 3.6
#6 -6.2 BAD -1.2 + 5 = 3.8
#7 -2.9 getting up there 2.1 + 5 = 7.1 bad
#8 -4.2 BAD .08 + 5 = 5.8 bad

according to these numbers 2, 3, 4, 7, 8 are all bad.. this is confusing or is it just me. :wtf:

These corrected numbers look quite different, and according to these numbers we now have 5 bad injectors, 2 on the edge, and one other that is starting to get up there. This is because like stated earlier balance rates are just an average of how far off each inejctor is from the average fuel flow which is your fuel rate. And if all the injectors are worn equally(like the above example), then the balance rates will stay close to each other but the fuel rate goes down. Once you learn to figure in the fuel rate to your balance rates, you will get much more accurate results of injector/engine health. But balance rates are just a test and not the end all be all of injector tests as it is just a small portion of what is going on and can be influenced by MANY other variables.

Lets do one more example to show how much balance rates can change once corrected to actual.

#1 -3.0
#2 0.4
#3 -2.8
#4 1.2
#5 -1.4
#6 -1.2
#7 4.5
#8 5.8

Now these numbers at first glance without figuring in the fuel rate show that #7 & #8 are out of the +/- 4 spec, but lets correct them for having a fuel rate of 3MM3. We need to add 5 to them again.

#1 -8.0 BAD
#2 -4.6 BAD
#3 -7.8 BAD
#4 -3.8 borderline
#5 -6.4 BAD
#6 -6.2 BAD
#7 -0.5 GOOD
#8 0.8 GOOD

So now #7 & #8 are the best of the bunch with corrected numbers, and we have 5 others bad with 1 borderline. This illustrates how critical it is to have the fuel rate to correct your balance rates to actual numbers, and why balance rates are worthless without knowing the fuel rate when they were taken.

Another good thing to do if you have the capability is to raise the rail pressure while checking the balance rates. Leaking ball seats will show up better at higher rail pressures than they do in the idle range, so by raising the rail pressure you can get a better idea of ball seat condition without doing a return rate test.

Keep in mind these numbers are for stock engines with stock tunes. If you have a modified tune it must use stock rail pressure at idle, and the fueling needs to be stock from 0-20MM3 of fuel(If in doubt put it back to stock). And if you have oversized inejctors you must have the tables corrected in the 0-20MM3 of fuel areas so that the puslewidths give the correct flow for each cell otherwise the balance rates will be inaccurate.

Also balance rates should not be confused with return rates. Return rates is the amount of fuel each injector returns to the tank during a 15 second cranking cycle, and involves a test set with 4 graduated cylinders to perform as well as some engine teardown to perform it. return rates are a much more accurate test of injector health since 01-10 DURAMAX injectors are a pressure differential valve. They open by opening the bypass port, and when there is a 1400-1500 PSI differential between the incoming fuel pressure and the pressure inside the inejctor it will open. This is why you need at least 1500 PSI for one to start as you have to have the pressure differential for the injector to open. Return rates tell you how well the bypass valves are sealing and if the ball seats are worn or not.


I have used this method for finding more bad LLY injectors than LB7's
 

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Discussion Starter #37 (Edited)
Excuse me if my math was off, but my numbers ARE correct for the corrected numbers. If your fuel rate is 3, and should be 8, then you need to add in the 5MM3 of difference. So if the balance rate is -2.1 with a fuel rate of 3, the ECM thinks it is injecting .9MM3 of fuel to that cylinder. It should be injecting roughly 8 MM3 of fuel, so the ECM is injecting -7.1 less than what it should be roughly, hence a corrected balance rate of a -7.1. So yes I should be adding -5 since it is down 5 from where it should be. This is why I put in examples so people could understand what I was trying to say(not to rip apart my ability to write a tech article).

I am NOT a tech article writer. I was trying to HELP others with info to help them dagnose issues with there trucks. This is info that was hard learned by myself from friends who worked at dealerships doing these trying to find ways to find out if it was injectors without having to break out the beaker set to do a return rate test right from the get go(and also mimimize cost to the customer to keep the bill down). I've used this info and test procedures to help countless others find out there injectors were bad, and finally decided to post it online to help others out since there always seems to be new threads popping up saying "truck smokes like crazy, but balance rates are fine", then come to find out it was injectors after all and if they had used corrected numbers like I posted, they would have found it right from the get go. Or swap out good injectors based on balance rates when they had several bad ones causing there issue instead of 1 or 2 like the balance rates showed at initial glance.
 

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This thread was a VERY good read.




So you're telling me a dirty cylinder is a good running cylinder? There is nothing that sounds right about that.

In my opinion this way of checking balance rates is extremely faulty. You claim I have 7 bad injectors yet my truck idles well, drives smooth, no surge, no smoke.........yet seven injectors are bad? Please explain that one.

Do you happen to sell injectors for a living?

Another issue is balance rates are not a reliable test for injector health anyways. A fuel return rate test is the proper way to do it. Lower compression in a cylinder can cause the balance rates to change and the change would have nothing to do with the injector.

Mods I would take a second look at having this as a sticky. This could lead people to replace a lot of injectors that do not need replaced.

I think what you are missing in all of this, just because the truck runs OK and the injectors aren't leaking profusely does not mean that they are in tip top shape.
 

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This thread was a VERY good read.







I think what you are missing in all of this, just because the truck runs OK and the injectors aren't leaking profusely does not mean that they are in tip top shape.

I don't think I am missing anything. The truck doesn't run just "OK", it runs great! My point is running the numbers the way described in this thread told me that I have 7 bad injectors and 1 good one. That is exactly backwards to reality. The one it says is good is the bad one(well not bad bad but worse than the others). and the other 7 are fine. They are not new so I know they are not perfect.

I'm not going to argue about this one anymore. I said what I had to say. People can take it as is or ignore it. It doesn't really matter to me. I just hate to see people spending a ton of money to replace a part that may not be bad. A return test is the only way to test for sure.
 

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Discussion Starter #40
I don't think I am missing anything. The truck doesn't run just "OK", it runs great! My point is running the numbers the way described in this thread told me that I have 7 bad injectors and 1 good one. That is exactly backwards to reality. The one it says is good is the bad one(well not bad bad but worse than the others). and the other 7 are fine. They are not new so I know they are not perfect.

I'm not going to argue about this one anymore. I said what I had to say. People can take it as is or ignore it. It doesn't really matter to me. I just hate to see people spending a ton of money to replace a part that may not be bad. A return test is the only way to test for sure.
And if you go back and reread my posts on this(or go to where I origanally posted it) you will see I said this is nothing more than a test to HELP determine where your problem is. I have NEVER said this is a definitive test as balance rates are nothing more than an indicator. And return rates are nothing more than one more test to help determine the problem. I did this write up to help others NOT to waste money on parts they don't need. There are to many posts of people saying there balance rates are perfect, or I have 1 out. They go in and replace just the one that's out and it doesn't fix it. They then get pissed off, say the trucks a POS, they'll never own another one again, bad mouth them to anybody that will listen, and get rid of it. When in reality they did the test wrong and thought they had found the bad inejctor when it was actually several being slightly off that was the problem.

I said fro mthe get go, it is nothing more than a DIAGNOSTIC TEST. It is not meant to be the end all be all, or used to throw money at a problem. But from my own persoannal experience I have helped others fix more than just a few trucks that others like yourself thought only needed 1 or 2 injectors that looked bad when it was actually 1 or 2 that looked fine on the balance rates.
 
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