FERMANATORS Injector diagnosis?

[cstephens93]

Ferman, I took a look at your post on the dieselplace in regards to properly checking injectors

Okay so heres what I got out of that post. Take the main fuel injection rate and subtract it from what it should be. On the LLY it should be 9mm3.

I drove my truck for about 15 minutes up to operating temp around 185 degrees, and both desired and actual rail pressure was 4.3 Kpsi. According to my edge, my MIFR was 4mm3. So I take 9mm3 and subtract 4mm3 which leaves 5mm3. So Im supposed to use 5 when looking at my injector balance rates.

Parked, in idle, my rates were as follows

Injector 1=-0.5 +-5 = -5.5
Injector 2=0.2 +-5 = -4.8
Injector 3=0.0 +-5 = -5
Injector 4=-0.8 +-5 = -5.8
Injector 5=2.5 +-5 = -2.5
Injector 6=-0.1 +-5 = -5.1
Injector 7=0.5 +-5 = -4.5
Injector 8=-1.8 +-5= -6.8

So this means all my injectors but injector 5 are bad?

I had my truck parked for about two hours. Drove home and when I got home,
at idle, parked, and operating temp my balance rates were as follows

Injector 1=-0.4 +-5 = -5.4
Injector 2=0.4 +-5 = -4.6
Injector 3=0.0 +-5 = -5
Injector 4=-0.8 +-5 = -5.8
Injector 5=2.6 +-5 = -2.4
Injector 6=-0.4 +-5 = -5.4
Injector 7=0.9 +-5 = -4.1
Injector 8=-2.0 +-5= -3

Once again it looks like the majority of my injectors are bad. All but 5 and 8?

Seem legit?

 

[messejme]

Keep in mind that the label used for the injector does not necessarily refer to that specific cylinder!

 

[cstephens93]

Keep in mind that the label used for the injector does not necessarily refer to that specific cylinder!

Yeah I figured. Still, I am in disbelief that I have that many "bad" injectors or that many injectors out of spec

 

[messejme]

I am not familiar with using that subtraction equation. I thought there was a specific # that should not be higher or lower than.

 

[cstephens93]

Well from what ferman says in this post,http://www.dieselplace.com/forum/63...nce-rates.html#/forumsite/20625/topics/576505

 

[Yngdmax92]

glad this got brought up, because it doesnt make any sense to me either. Maybe someone on here could explain more about it?

 

[cstephens93]

glad this got brought up, because it doesnt make any sense to me either. Maybe someone on here could explain more about it?

Are you familiar with Fermanators post?

 

[messejme]

I read ferm's post but like he said this is an equation he and his friend came up with. If it works then great but why isn't this a GM standard approved procedure?

 

[cstephens93]

I read ferm's post but like he said this is an equation he and his friend came up with. If it works then great but why isn't this a GM standard approved procedure?

Good question. If he and his friend are correct, I have some saving to do

 

[andy-stevenson]

I think he said to use 8mm3, not that it makes much of a difference. Your truck was up to temp when you checked? Stock tune?

 

[c20elephant]

The only time my truck might come up to operating temperature in 15 minutes is in August after sitting till noon at 100 degrees...

 

[cstephens93]

I think he said to use 8mm3, not that it makes much of a difference. Your truck was up to temp when you checked? Stock tune?

My Edge Insight was reading 183-188degrees. I was on my DSP position 1 tune which is just a heavy tow tune. The other tunes are , light tow, DD/Econ 120hp, Street 175hp, and Race 220hp



My estimation of 15 minutes may be skewed, but i was stuck in some heavy traffic, hopped on the interstate, did a lil more driving, and reached my destination. Read 185 degrees or so

 

[THEFERMANATOR]

I responded to you over at DP(haven't bee nther today to see if you responded yet as I come here 1st). At idle you should see roughly 8-9Mm3 of fuel for the fuel rate. Check as many trucks as you want, and you will find this is pretty damn close to what you will find for a "HEALTHY" truck. The ECM when figuring balance rates simply determines how much fuel each injector is injecting +/- of the average of the 8 cylinders. The fuel rate is the average of all 8, and the balance rate is how far off that particuliar injector is from the fuel rate or average of all 8. So if multiple injectors are bad, it can throw off the average and bring the fuel rate for the whole engine down. And this information WAS from a friend who worked at a dealership, and got this info FROM the GM techline, so GM IS aware of this procedure since it came from a GM higher up. As I also said over at DP, if your not having problems, then don't concern yourself with it. MANY factors can effect balance rates, and if ALL your injectors are going at the same time it can throw the numbers off. The engine can go a LONG time before injectors get bad enough to cause an issue, but I shared this info to try and help others without access to a return rate test kit to find the bad injector. And lastly, make sure you are using an ACCURATE scanner. I know I have had some readings that looked horrible on the customers display, but plug in my V2 and get completely different data from the truck. It wasn't long ago we were using a friends code reader that had basic scanning ability, and it was showing something ridiculous like 98MPA of rail pressure at WOT. Connect the V2, and it showed the desired 165 I was calling for. Or another guy just last week with a PREDATOR seeing only 18K PSI when he should have been seeing closer to 26K PSI.

 

[cstephens93]

I responded to you over at DP(haven't bee nther today to see if you responded yet as I come here 1st). At idle you should see roughly 8-9Mm3 of fuel for the fuel rate. Check as many trucks as you want, and you will find this is pretty damn close to what you will find for a "HEALTHY" truck. The ECM when figuring balance rates simply determines how much fuel each injector is injecting +/- of the average of the 8 cylinders. The fuel rate is the average of all 8, and the balance rate is how far off that particuliar injector is from the fuel rate or average of all 8. So if multiple injectors are bad, it can throw off the average and bring the fuel rate for the whole engine down. And this information WAS from a friend who worked at a dealership, and got this info FROM the GM techline, so GM IS aware of this procedure since it came from a GM higher up. As I also said over at DP, if your not having problems, then don't concern yourself with it. MANY factors can effect balance rates, and if ALL your injectors are going at the same time it can throw the numbers off. The engine can go a LONG time before injectors get bad enough to cause an issue, but I shared this info to try and help others without access to a return rate test kit to find the bad injector. And lastly, make sure you are using an ACCURATE scanner. I know I have had some readings that looked horrible on the customers display, but plug in my V2 and get completely different data from the truck. It wasn't long ago we were using a friends code reader that had basic scanning ability, and it was showing something ridiculous like 98MPA of rail pressure at WOT. Connect the V2, and it showed the desired 165 I was calling for. Or another guy just last week with a PREDATOR seeing only 18K PSI when he should have been seeing closer to 26K PSI.

Speaking of you mentioning the desired 165mpa.....was that on an LBZ? Or does it matter what engine it is. I have read that the LLY only calls for 160mpa. I had another scanner today hooked up to it and the most it would allow me to raise the rail pressure was 160mpa

 

[THEFERMANATOR]

Speaking of you mentioning the desired 165mpa.....was that on an LBZ? Or does it matter what engine it is. I have read that the LLY only calls for 160mpa. I had another scanner today hooked up to it and the most it would allow me to raise the rail pressure was 160mpa

As far as I know, the highest you can command with a bidirectional scan tool on any gen is 160. The 165 was on an LLY with a modified tune in it. I felt bold and decided to bump the rail pressure a touch on a mostly stock LLY trying to clean up ALL the smoke.

 

[S Phinney]

What if the truck at idle sees more than 8 to 9mm3. Like 15 mm3?

 

[messejme]

Thanks for sharing this info with us Ferm. This equation is new to me so you elaborating on it is appreciated.

 

[Frankin_truck]

Thanks for the info Ferm. I don't know why. As soon as you mention poor balance rates, everyone assumes bad injectors. There are more things that can affect a balance rate than just the injector. Like the old saying "if it ain't broke, don't fix it "

 

[cstephens93]

I dont think anythings wrong with my truck. but like posted above, when i see poor balance rates, I immediately think bad injectors

 

[THEFERMANATOR]

What if the truck at idle sees more than 8 to 9mm3. Like 15 mm3?

I had one do this, turned out he had 7 plugged injectors. Truck finally just up and quit running once the balance rates all kept climbing and the fuel rate got up to about 18MM3 of fuel. Also be CERTAIN if your using this method on a truck with oversized injectors, or modified engine, that these numbers go out the window. If the injector pulse width table isn't corrected PERFECTLY, then the numbers will obviously be off. And delipped pistons, changed compression, porting, and so on can also effect how much fuel the engine needs at idle. And like others said, this is just another peice of the puzzle. You could have weak compression, or who knows what else causing issues that show up in balance rates.