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Testing injectors while in the truck, thoughts and questions

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Hi forum. 210k miles on original injectors with stock, 10 micron fuel filtration. My symptoms have been occasional rough idling as if running on 5 cylinders and occasional slightly longer starting than normal usually accompanied by a small puff of smoke. Usually clears itself with heavier loading or some spirited driving. I’ve used injector cleaners on occasion for periods as long as a couple months, but I couldn’t discern a significant difference.

I’ve explored this same subject in the past and have even posted on this forum about it. Some very knowledgeable people replied saying that based on mileage at the time and the use of only stock fuel filtration ( 10 micron ), that it was very likely worn injectors with less effective sealing ( resulting in leakage ) and less effective spray pattern, etc.

Given how the engine still seems to run well other than occasional hiccups above and what others have said about how long they’ve been able to run on original setups I’m interested in first being able to confirm problematic injectors. The scientist in me wants to measure a problem...

Towards that end I’m reviewing the limited ways to test the injectors while in the truck and hoping others can share their experience and comment on my thoughts...

-The cylinder contribution test ( based on measuring duty cycle of injection ?) is supposedly unreliable with immediate subsequent tests having varied results ? Can it be repeated enough times to actually learn something about condition of injectors or are there variations on this test that do reveal the condition of injectors ?

-The injector kill test is a good way to verify that an injector is working poorly or not at all, but seems to tell relatively little about injectors that perform moderately well or better ? It would seem a good test to perform when I have my intermittent 5 cylinder symptoms to isolate which injector(s) is problematic.

-I’d seen somewhere about measuring injector performance based on crankshaft speed and thinking about using my oscilloscope to measure crankshaft speed ( CKP ) and then performing some spreadsheet calculations on the results, but I’ve now read that this ECM (CM848) will compensate duty cycle to regulate engine speed so it seems this wouldn’t be a reliable way to test ? I suppose rather than comparing crankshaft speed of each injection ( using the fastest injector crankshaft speed as a reference ) perhaps one could compare crankshaft speed against duty cycle ( positive % ) to determine how effective injector pulse is ? I suspect somebody here knows more about this.

-In the end I come back to the Mastertech video series that came out when the 3rd gen. trucks were released ( linked below ). Being a shared low-pressure injector return ( without individual injector returns ) it seems this test requires capping off individual injectors and measuring the shared return fuel flow to see if the capped off injector brings fuel amount within specification or for comparing return amounts of each injector ? Of course, this is only about leakage ( leak-off ) and says nothing about other injector performance like spray pattern.

*As a side note this post reminds me of a free “Leak-off testing of solenoid diesel injectors” technical video that I watched at https://www.ourvirtualacademy.com/. They offer a free 14 day trial with 3 free videos including this video which was amazing for me for the hydraulics behind fuel injector operation, understanding injector mechanics in general, potential problems with injectors particularly with contamination. There are some good high magnification photos of contamination. I have nothing to do with website.

*Mastertech video mentioned above:

Thank you, Sven
 
only thing I can say is common rail engine management is so good at compensating for a weak cylinder that it can be quite the chore to diagnose and found it was easier to replace all the injectors at the same time than to spend an inordinate amount of time and effort troubleshooting.

you can help yourself with a cylinder cutout test if you can put the engine under more load by putting it in gear and turning on the AC but as I said that darn puter is pretty good at compensating for a weak injector and sometimes you aren't sure which one is the culprit.

In the end if it runs good otherwise I'd just live with it until it becomes a problem.
 
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only other thing I might add is if you are pretty sure which injector it is ( hopefully it is in the front LOL ) you can always swap the bad injectors around with a known good injector and see if the problem moves to the swapped cylinder.

Also had some luck identifying a weak cylinders using an Infrared tester on exhaust ports, This works best when the engine is cold and isn't always practical depending on how EZ it is to get a shot at each exhaust port.
 
The best way to test injectors in the truck is by capping off individual injectors just like the Master Tech video shows. It does not confirm spray pattern, only internal injector problems.
 
Spend your time buying and installing new injectors, you've gotten your moneys worth out of those original ones. Put some better filtration on it 2micron.
 
Stick filtration should be 7µ. What filter are you running?

210K miles is worth just getting new injectors and better fuel filtration.
 
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