LB7 injector test

[jjcsnlynn]

Wow, were these easy to check. It's good to know that my friends friend has one of these (Snap On Modis).

Here are my readings. Do I have anything to worry about?

Injector CMD: (Engine cold as hell...32 degrees)
1-5: .5
6: .6
7-8: .5

After engine warmed for about 5 minutes:
1-5: .3
6: .4
7-8: .3

Balance Rates (Engine initial start at 32 degrees)
1: -.1
2: 0
3: .1
4: 0
5: -.1
6: .6
7: -.2
8: -.1

After 5 minutes of Idle
1: -.1
2: .1
3: .1
4: .1
5: 0
6: .3
7: -.2
8: 0

ACT FRP is 42. Is that the Fuel pressure?

I also got a P0380- glow plug code. I monitored and the relay was going on then off, but the voltage stayed at Zero
- Is there a glow plug fuse? (don't have a manual yet).

Do I have anything to worry about on the injectors? Can I try the cleaner and lubricant in the tank method? The truck runs fine. Yesterday I started it after 2 weeks of sitting in 10-30 degree weather and there was only a little white coming from the exhaust. It only lasted about 5 minutes and then went away. I'd also not sure if it was smoke or just steam. It was 35 degrees out when I started.

[THEFERMANATOR]

Balance rates is just a small part of the picture when it comes to injector health. Return rates are MUCH more important in my opinion, but this is the test that requires engine teardown and the chemistry set to do.

[DmaxMaverick]

No flags on your PWM and balance rates. Actually, they look too good to be true. I'd suspect the test procedure and/or conditions during the test. 5 minutes of idle during cold weather (and often in hot weather) is hardly enough to step up the balancing and pilot modes. It's best done after a good, hard run (engine/tranny up to full operating temp), with varying engine load conditions.

ACT FRP is Actual Fuel Rail Pressure. Useless without the "desired" value. The value should be stable, and track closely with the desired. Again, it won't tell you much on a "cold" engine.

Glow plugs -- Either they are unplugged, you have less than 3 working, or the controller (relays) have failed (or the scanner isn't reading the circuit properly). Check the harness connections, and each plug. Federal smog trucks have a known failure issue of the GP and heater relays. If they're the problem, replace the entire controller. The individual relays cost 4x the price of the complete controller. Healthy Duramax engines will start with no glow plugs down to very cold temps (below zero), although it may be more "eventful" as it gets colder. P0380 can also indicate an intake heater failure.

The little bit of white smoke from the exhaust sounds normal for the conditions. Probably steam from accumulated intake/exhaust moisture. Very common after sitting a long time in the very cold. If it has California smog (EGR), it can take a bit for it to cycle properly after a long dormant period (a week or more). The lack of glow plugs and/or intake heater can exaggerate all of the above until the temp starts to come up.

You should be using a good fuel additive already. Fuel quality, no matter where you get it, should always be suspect.

[Kennedy]

Balance rates is just a small part of the picture when it comes to injector health. Return rates are MUCH more important in my opinion, but this is the test that requires engine teardown and the chemistry set to do.

Agreed. Balance rates are overrated. They are simply the first step in diagnosing an issue much like taking a person's body temp.



No flags on your PWM and balance rates. Actually, they look too good to be true. I'd suspect the test procedure and/or conditions during the test. 5 minutes of idle during cold weather (and often in hot weather) is hardly enough to step up the balancing and pilot modes. It's best done after a good, hard run (engine/tranny up to full operating temp), with varying engine load conditions.

ACT FRP is Actual Fuel Rail Pressure. Useless without the "desired" value. The value should be stable, and track closely with the desired. Again, it won't tell you much on a "cold" engine.

Glow plugs -- Either they are unplugged, you have less than 3 working, or the controller (relays) have failed (or the scanner isn't reading the circuit properly). Check the harness connections, and each plug. Federal smog trucks have a known failure issue of the GP and heater relays. If they're the problem, replace the entire controller. The individual relays cost 4x the price of the complete controller. Healthy Duramax engines will start with no glow plugs down to very cold temps (below zero), although it may be more "eventful" as it gets colder. P0380 can also indicate an intake heater failure.

The little bit of white smoke from the exhaust sounds normal for the conditions. Probably steam from accumulated intake/exhaust moisture. Very common after sitting a long time in the very cold. If it has California smog (EGR), it can take a bit for it to cycle properly after a long dormant period (a week or more). The lack of glow plugs and/or intake heater can exaggerate all of the above until the temp starts to come up.

You should be using a good fuel additive already. Fuel quality, no matter where you get it, should always be suspect.

I don't trust 3rd party scan data unless it can be correclated to a Tech 2. Sampling rates, averaging times etc tend to make the data differ and I definitely agree with these being "too good to be true" especially when not full temp. Get it up to temp and test again. Also compare to a Tech 2.


We are not trying to be naysayers here, just realistic.

[DmaxMaverick]

Agreed. Balance rates are overrated. They are simply the first step in diagnosing an issue much like taking a person's body temp.




I don't trust 3rd party scan data unless it can be correclated to a Tech 2. Sampling rates, averaging times etc tend to make the data differ and I definitely agree with these being "too good to be true" especially when not full temp. Get it up to temp and test again. Also compare to a Tech 2.


We are not trying to be naysayers here, just realistic.

I absolutely agree. It takes a lot more than just reading numbers on a display to get a clear picture. The Tech II is the benchmark for reading values, no doubt. Other scanners are just as accurate, but may not display the values on the same scale or in the same context. It takes some extensive comparison (and a Dick Tracy decoder ring) to get accurate values to show themselves. Most end-users, and even a large number of tech's, don't/won't take the time to do this, therefor are taking action on unreliable data. In the end, I recommend the same as you. Unless a person has extensive experience with several scanners, including the Tech II, then the Tech II should be the only reliable source for diagnosis. It isn't rocket science. Just almost.

[THEFERMANATOR]

The snap-on scanner is known to NOT be able to corectly communicate with the DURAMAX ECM, so test data from it should be taken as pure specualtion. They are known to show anything from numbers too good to be true to numbers like -380 for teh balance rates. Also EFILIVE is GREAT tool for checking balance rates, but there is some confusion right now as to wether or not it displays the correct balance rate for which cylinder. It seems as though they numbered the balance rates and injector kill functions according to there order in the firing order rather than engine order. A TECH 2 is the ONLY proven tool for working with a DURAMAX.

[jjcsnlynn]

You guys are starting to make me worry. :eek: It seems the dealer has a corner on the market for testing the Duramax, and in reading numerous posts, the dealers don't know what they are doing when it comes to injectors.

Since my truck seems to be running find, I may just stick my head in the mud and forget about all this until I see symptoms.

[NutNbutGMC]

You guys are starting to make me worry. :eek: It seems the dealer has a corner on the market for testing the Duramax, and in reading numerous posts, the dealers don't know what they are doing when it comes to injectors.

Since my truck seems to be running find, I may just stick my head in the mud and forget about all this until I see symptoms.One suggestion if you so choose to further, find a dealership or other mechanic resource with specific and trained GM diesel knowledge. Just because a dealer has a mechanic, doesn't mean they know what they are doing. Been down that road with three other LB7 injector issues back in 2001 and 2002.

The guys in this thread are the kind of resources that I refer (excluding myself). They live and breath diesel.....

[Kennedy]

If it's runing good and no symptoms then no need to fix it. Simply follow this advice:

http://www.kennedydiesel.com/docs/Duramax%20Injector%20Failures.pdf

[James doe]

hey
Im enrolled in an automotive program in northern wisconsin and just happen to be in an engine performance class when my 02 2500 started to idle rough. The truck has 219XXX miles on it but was previously owned by my father in which he bought new. Ive had the tech 2 on it and checked the balance rates and did a clylinder power balance test. The balance rates all came out to to .0 which i find hard to believe and the clyinder power balance test each clyinder dropped similar rpm. All testing was done after a half hour of driving. Three things have come to mind tho

ECT sensor never got north of 163 degrees with a temp of 10 f outside and the winter grill cover on. I plan on replacing thermostats and flushing coolant on friday. I believe engine temp that 20 degrees under what the thermostats range are could have an effect on readings from the tests. Am I correct on this?

Also there is not a factory tune on the dsp5 switch which I plan to get one this weekend as the tunes from day one have seemed just slightly rougher but nothing near what the truck is like now when the engine temp gets to what it runs at.

The boost sensor was also reading 13psi at idle. Idk if this has something to do with the way it was tuned but I also have a boost gauge that never read above 22 psi when it was in the truck. I had to send the gauge back and shld be getting it back soon. There were codes that didnt turn the MIL on that where for Turbocharger over boost and turbocharger system performance. The sensor reads from 13psi and up so ima assuming this is why the codes where thrown. Can having the boost line running in the cab without the gauge attached have an effect on boost sensor readings?

almost forgot truck had all 8 injectors replaced at 110000 under waranty and care has been taking to keep on fuel filters and use fuel additives for the most part but seems to me that most people out there have had them go under a pattern. Truck is also a federal emissions truck.

Thanks for any input

[JohnC]

The PCM reads manifold absolute pressure. Engine off should get you about 14.7 psi at sea level. 13 psi at idle is probably about right.

Did you plug the line coming into the cab? If so, it will have no effect. If not, probably no noticeable effect anyhow.

[DmaxMaverick]

hey
Im enrolled in an automotive program in northern wisconsin and just happen to be in an engine performance class when my 02 2500 started to idle rough. The truck has 219XXX miles on it but was previously owned by my father in which he bought new. Ive had the tech 2 on it and checked the balance rates and did a clylinder power balance test. The balance rates all came out to to .0 which i find hard to believe and the clyinder power balance test each clyinder dropped similar rpm. All testing was done after a half hour of driving. Three things have come to mind tho

ECT sensor never got north of 163 degrees with a temp of 10 f outside and the winter grill cover on. I plan on replacing thermostats and flushing coolant on friday. I believe engine temp that 20 degrees under what the thermostats range are could have an effect on readings from the tests. Am I correct on this?

Also there is not a factory tune on the dsp5 switch which I plan to get one this weekend as the tunes from day one have seemed just slightly rougher but nothing near what the truck is like now when the engine temp gets to what it runs at.

The boost sensor was also reading 13psi at idle. Idk if this has something to do with the way it was tuned but I also have a boost gauge that never read above 22 psi when it was in the truck. I had to send the gauge back and shld be getting it back soon. There were codes that didnt turn the MIL on that where for Turbocharger over boost and turbocharger system performance. The sensor reads from 13psi and up so ima assuming this is why the codes where thrown. Can having the boost line running in the cab without the gauge attached have an effect on boost sensor readings?

almost forgot truck had all 8 injectors replaced at 110000 under waranty and care has been taking to keep on fuel filters and use fuel additives for the most part but seems to me that most people out there have had them go under a pattern. Truck is also a federal emissions truck.

Thanks for any input

The boost reading is probably correct. The PCM instrumentation reading for air pressure is PSIA, not PSIG. Meaning, it starts at 14.7 PSI at sea level. So, your 13.x reading is zero PSIG (or close enough, it doesn't matter). PSIA = PSI Atmosphere, PSIG = PSI Gage.

[Kennedy]

hey
Im enrolled in an automotive program in northern wisconsin and just happen to be in an engine performance class when my 02 2500 started to idle rough. The truck has 219XXX miles on it but was previously owned by my father in which he bought new. Ive had the tech 2 on it and checked the balance rates and did a clylinder power balance test. The balance rates all came out to to .0 which i find hard to believe and the clyinder power balance test each clyinder dropped similar rpm. All testing was done after a half hour of driving. Three things have come to mind tho

ECT sensor never got north of 163 degrees with a temp of 10 f outside and the winter grill cover on. I plan on replacing thermostats and flushing coolant on friday. I believe engine temp that 20 degrees under what the thermostats range are could have an effect on readings from the tests. Am I correct on this?

Also there is not a factory tune on the dsp5 switch which I plan to get one this weekend as the tunes from day one have seemed just slightly rougher but nothing near what the truck is like now when the engine temp gets to what it runs at.

The boost sensor was also reading 13psi at idle. Idk if this has something to do with the way it was tuned but I also have a boost gauge that never read above 22 psi when it was in the truck. I had to send the gauge back and shld be getting it back soon. There were codes that didnt turn the MIL on that where for Turbocharger over boost and turbocharger system performance. The sensor reads from 13psi and up so ima assuming this is why the codes where thrown. Can having the boost line running in the cab without the gauge attached have an effect on boost sensor readings?

almost forgot truck had all 8 injectors replaced at 110000 under waranty and care has been taking to keep on fuel filters and use fuel additives for the most part but seems to me that most people out there have had them go under a pattern. Truck is also a federal emissions truck.

Thanks for any input

When the balance rates read 0 there is something wrong and it is not balancing at all. It could be in the programming would be my first guess.

Go back to the programming or at least put the injector pulse tables back to stock.

Having to send the boost gauge back I assume there was a problem with it? Auto Meter brand?

The overboost code is something that needs to be dealt with in the ECM programming.

One common thread here: programming...