injector info on scanner tool

[corn_bread]

wanting to make sure i have correct data. think i have an injector going out. have a labor knock on sounds like one cylinder and trying to pin point which cylinder. can primer till bulb is hard and will go away for a while. replaced all seals and hoses at primer pump. any help appreciated. 07 chevy 3500 6.6 LBZ. scan file of what i have is attached.

[dhoagland]

I'm not 100% sure how accurate the balance test is, or exactly what you are asking...
I didn't think this test should run until engine was up to operating temp, but you have it running at 99 degrees ECT...

I'm assuming you think you have a fuel knock.
Have you tried to cut the cylinders out and see if you can isolate the noise to one?

[TheMechanic]

I do injector balance tests on a regular basis for a few decades It works well in isolating bad injectors. It will not determine good or bad spray patterns but as a diagnostic tool it is fantastic. Either using a scan tool for the diagnostic or one of my injector drivers on those that do not. As in early model stuff.

[dhoagland]

I do injector balance tests on a regular basis for a few decades It works well in isolating bad injectors. It will not determine good or bad spray patterns but as a diagnostic tool it is fantastic. Either using a scan tool for the diagnostic or one of my injector drivers on those that do not. As in early model stuff.

Good to know
Is the test supposed to be able to initialize before full operating temp? (in his log it shows under 100 degrees)

[TheMechanic]

Wow I feel like a dumbass. i thought we were talking gas engines.
Anyways for the Duramax I use the balance rates. Yes it can be done on a stone cold engine. Here is the actual diag
Fuel Injector Balance Test with Tech 2
Diagnostic Instructions
Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Review Strategy Based Diagnosis for an overview of the diagnostic approach.
Diagnostic Procedure Instructions provides an overview of each diagnostic category.
Circuit/System Description
The fuel injector balance test is performed when a misfire, knock, excessive smoke, or rough running condition exists with no electrical DTCs. This test uses the Balance Rate and Cylinder Power Balance test to identify cylinders that are not producing the designed power output. The balance rate adjustments are utilized by the engine control module (ECM) only at idle. The balance rates are the fuel adjustments for each individual cylinder based on the variations in engine crankshaft speed. The balance rates will change depending on if the transmission is in Neutral or Drive. During the Cylinder Power Balance portion of the test, the ECM turns OFF individual injectors while the engine is running. The ECM adjusts for the drop in engine RPM during cancellation and may not change on the scan tool display. The lack of power at the cancelled cylinder will feel like a misfiring cylinder or vibration. If a fuel injector is turned OFF and there is a no difference felt when compared to the other cylinders, that cylinder is identified with the concern. If the customer concern occurs during idle or during off-idle tip in acceleration, the balance rates are used to identify the cylinder with a fault related to the fuel injector or engine compression.

Diagnostic Aids
The Cylinder Power Balance Test may be performed at any engine speed or load from idle to wide open throttle (WOT). There is a 5-minute time limit for each test.
A high balance rate may be caused by a fuel injector or cylinder compression only if the ECM can control fuel pressure.
Circuit/System Verification
Important: If any DTCs other than DTC P0300–P0308 are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle.

Start and run the engine until the coolant temperature is more than 82?C (180?F). Turn OFF all accessories.
Perform the fuel pressure regulator test, refer to Fuel Pressure Regulator Diagnosis.
With a scan tool, command the Balance Rate Monitor ON. Balance rates should be between +4 mm? and −6.9 mm? in Park or Neutral. Balance rates outside the range may indicate contaminated fuel. Refer to Contaminants-in-Fuel Diagnosis.
Important:

The Cylinder Power Balance Test must be performed under the conditions for which the customer concern occurred.
Do not operate the cruise control during this test. Cruise control may cause a brief surge of engine speed after the completion of the test.
Perform the Cylinder Power Balance Test with a scan tool. During cylinder cancellation a noticeable power difference will feel like a misfiring cylinder or vibration.
Circuit/System Testing
Important:

You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.
A fuel injector leak into the combustion chamber may result in mechanical damage to the cylinder. If any fuel spray comes out of a glow plug hole during the compression test, replace the fuel injector of the affected cylinder.
If fuel vapor is emitted during the engine compression test, replace the affected fuel injector and inspect for fuel contamination. refer to Contaminants-in-Fuel Diagnosis.
Perform the engine compression test. Refer to Engine Compression Test.

If the compression indicated any of the cylinders had low compression, refer to Symptoms - Engine Mechanical.
Important:

Failure to correctly identify the cylinder positions may result in the replacement of the wrong injector.
During replacement of the injectors, inspect the inlet and outlet fittings for corrosion or contamination. Refer to Contaminants-in-Fuel Diagnosis.
If the engine did not have low compression on any of the cylinders, replace the fuel injectors on the cylinders that had low cylinder power contribution, high balance rates, or a noise/smoke change during cancellation.

Forgot to add. I will also command the Fuel Rail Pressure to max pressure approx 160-180 mpa. I will get a nice Dodge noisy idle telling me the high pressure fuel system is capable of getting high pressure fuel to the injectors. Oh and last last GM diesels are junk. The new Bosch injectors are better. We used to pile those injectors up by the hundreds at the dealer. Glad I was a driveability tech and not the "smelly diesel guy". Funny now that's all I work on for Uncle Sam.

[dhoagland]

Thank You!

[corn_bread]

Thank you both