Chevy and GMC Duramax Diesel Forum banner

Take a look at my balance rates.what do you think?

5K views 11 replies 4 participants last post by  parkly761 
#1 ·
I just bought an 03 GMC 2500HD with 240k. Last week , I got a Super Deal Because the dealer told the previous owner that he needed 5 injectors. Now I will tell you when I test drove it I believed it.. It would barley get past 70mph. I immediately started a sea foam treatment and ran the crap out of it. It wad a totally different truck within 2days and is still improving dramatically.

Now it only smokes after a long time idling. I found out the scanner I have at work will run a boat load of tests. The only one I know to run right now is balance rate test. Unfortunately I didn't test it when I bought the truck. These results are a week later. 2 bottles of seam foam through a new fuel filter and two through a full tank of fuel and one through the crankcase before the oil change on sat. The where and still aren't any signs of fuel smell,paper towel test in the oil.

Now I have read plenty on balance test tolerance and for warranty purposes I have seen them to be +- 4 in park and +- 6 in drive w\brake applied accessories off. But now I have also read the true tolerance for good performance is +-2.

Here are my current specs in park and in drive both with brake applied and accessories off @ operating temp.

Park
 

Attachments

See less See more
1
#3 ·
Try cleaning your injectors...


From the DF mobile informer-
 
#4 ·
They aren't horrible, but I'd watch the high numbers.

#1 is leaking, or intentionally adding fuel to counter a clog
#6 is clogged, or countering a leaking injector
#7 is leaking, or intentionally countering a clog.

As Frank said, try a cleaning and see what the numbers do. The clog may clear, or the sticking injectors may free up. A leaking injector may get worse, but it will definitely point to the problem.
 
#5 ·
I have been using seafoam to clean the system this past week. 2 bottles through new fuel filter. 2bottles to full tank of fuel. I just finished going through a gallon of seafoam to 4 gal of fuel today.

Should I try a different product or method? Or both?
 
#6 ·
Well you may be making it worse running that much cleaner through the tank... It will send more garbage in the tank to the injectors. The filter wont catch it all...

There is a DIY injector cleaning process in the How to section of the forum. Read up on that and it will answer all your questions about the cleaning of injectors.
 
#7 ·
Thanks I will be checking that section out tonight. I didn't even think about the trash. But had planned on changing the fuel filter again this weekend.
 
#8 ·
Okay so I did the cleaning today. Here are before,after and after test drive. What gets me is it looks like the went backwards after my test drive. Could this me caused because of crap in the lines? This is before cleaning.
 

Attachments

#11 ·
Well I did some more research and it turns out that my balance rates didn't get worse. If you look at the before cleaning and after cleaning my fuel flow rate is 5 when it should be 8 or 9 and in the photo after test drive my flow rate is 9 at idle. This is what I found , I don't know if a Mod would like to sticky this or not.




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(the displayed fuel rate is 5MM3 of fuel low, so it is -5 off). So lets see the corrected numbers.

#1 -7.1 BAD
#2 -3.6 borderline
#3 -5.8 BAD
#4 -3.8 borderline
#5 -6.4 BAD
#6 -6.2 BAD
#7 -2.9 getting up there
#8 -4.2 BAD

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 injector 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.
 
#12 ·
Question. I can only get a fuel rate in gallons per minute. When I convert that to mm3 it gives me a number in the thousands. What am I doing wrong?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top