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  #1  
Old 08-07-2011, 05:32 PM
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diagnosing sticking injectors

Well, my truck starts terribly. It needs to idle for about 5 minutes before it will even move under its own power. It shakes, blows black smoke, and occasionally stalls shortly after starting. Once it's up to temperature, it runs like a top. FICM voltage is rock solid at 48.5-49 (keoe, cranking, koeo). When it first starts if you read the DTC's you get cylinder 2 contribution/balance fault, and cylinder 4 contribution/balance fault. I'm going to replace those 2, as I'm sure they're the worst of the bunch. Is there any other way of diagnosing the exact cylinders? Those are the only 2 that fail the contribution test, but with the way it's running, it sure seems like more than 2 are experiencing stiction. After I replace those 2 I'm going to switch to t6/rev-x, and re-test.
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Old 08-07-2011, 06:12 PM
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I can't speak for the effectiveness of aftermarket scan tools, simply by virtue of the fact that I never use them (because I use the Ford IDS obvously). But if you're getting cylinders #2 and #4 setting low contribution balance faults, you're lucky. The way I diagnose faulty injector(s), is to start the engine up when it's completely cold-soaked (sat overnight since last running), with the IDS power balance graph screen up and ready to view the "low" cylinders as soon as the engine is started, and FICM compensation disabled (a feature that is likely unavailable with aftermarket scan tools). So far, I haven't had any trouble pinpointing weak/faulty injector(s) with this method. It doesn't hurt to have the "blue spring" pressure regulator spring installed either, which I'm sure you already have by now, if you are a "veteran" member of this site.
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Old 08-07-2011, 06:24 PM
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I do indeed have a blue spring installed, and a fuel pressure reading of 66psi at idle, lowest it will get to is 55 at WOT with my extreme tune loaded.

Cylinders 2&4 are the only 2 that fail the contribution test on cold starts, cylinder 4 will clear up within a minute, while 2 will persist until it's up to temp. I was planning on putting the injector swap off until I needed to do headgaskets/studs/oil cooler, but by the looks of it that could be a while, and the cold starts are definately getting worse. I doubt it'll even start once winter comes.

I guess the main question I have for you, as I'm sure you have a lot of experience with sticking injectors, is:

Do you believe 2 injectors (on the same bank) sticking would be sufficient to cause the lack of power I'm describing? I'm torn. Having driven many a truck with several bad injectors, this feels more like 2 being completely beat, with several others not performing optimally. It is with the latter that I'm looking for tips.
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Old 08-07-2011, 06:40 PM
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You know what's funny? I just literally came back from someone's house hours ago, diagnosing two faulty injectors with almost the exact symptoms you described. And I can tell you that having two cylinders not pulling their weight will definitely adversely affect how it drives. This should be a no brainer. Any more than two cylinders down, and you'll be lucky if the engine even fires up.
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Old 08-07-2011, 06:44 PM
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*sigh*

I need to find one more injector.

I just hate to go in there and only replace 2. I was hoping for a definitive test to determine if any of the others aren't pulling their weight. I KNOW 2 and 4 are bad, but The fact that it literally won't even attempt to move for 5 minutes makes me believe there are more that have failed but still work well enough to pass the contribution test. Thanks again!
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Old 08-07-2011, 06:59 PM
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What exactly do you mean by "definitive"? If you run a KOEO Injector Buzz test, and that returns a PASS result, what does THAT tell you? I don't about everyone else, but what it tells ME, is that the FICM and FICM harness are good. It also tells ME the injectors are "good" on the ELECTRICAL end (you can ohm out the OPEN +/- and CLOSE +/- to verify this). But, it doesn't tell me squatty pot about the MECHANICAL end of the component. Nor am I able to give you any definitive causes for the failures themselves beyond the usual wear and tear with use. I can tell you as a tech, that low fuel pressure, poor fuel quality, lack of maintenance only greatly accelerates and increases the likelihood for failures though. But I can also tell you that most of the time, removal will not give you any visual clues for failure unfortunately. Is that what you meant by definitive, some thing/test that you can run that will give you a VISUAL indication of weak performance/failure? Does your scan tool not give you a power balance graph that you can view? Is the FICM compensation cancel feature available on your scan tool?
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Old 08-07-2011, 07:06 PM
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Quote:
Originally Posted by m-chan68 View Post
What exactly do you mean by "definitive"? If you run a KOEO Injector Buzz test, and that returns a PASS result, what does THAT tell you? I don't about everyone else, but what it tells ME, is that the FICM and FICM harness are good. It also tells ME the injectors are "good" on the ELECTRICAL end (you can ohm out the OPEN +/- and CLOSE +/- to verify this). But, it doesn't tell me squatty pot about the MECHANICAL end of the component. Nor am I able to give you any definitive causes for the failures themselves beyond the usual wear and tear with use. I can tell you as a tech, that low fuel pressure, poor fuel quality, lack of maintenance only greatly accelerates and increases the likelihood for failures though. But I can also tell you that most of the time, removal will not give you any visual clues for failure unfortunately. Is that what you meant by definitive, some thing/test that you can run that will give you a VISUAL indication of weak performance/failure? Does your scan tool not give you a power balance graph that you can view? Is the FICM compensation cancel feature available on your scan tool?
Definitive, for me at least, would be some measurement of the spool valve reaction time. Electrically all the injectors test fine. I'd be willing to bet they have accumulated varnish/carbon deposits left from conventional oil. Having removed faulty injectors before, I know externally they will look fine. If it was a 7.3 I'd pull them apart and check the plungers/barrels for scoring, and check the armature clearance. I guess I was just hoping someone had a trick I hadn't heard about.
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Old 08-07-2011, 07:19 PM
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Originally Posted by dazdillenger View Post
If it was a 7.3 I'd pull them apart and check the plungers/barrels for scoring, and check the armature clearance. I guess I was just hoping someone had a trick I hadn't heard about.
Ahhh yes. But 7.3L injectors are much bigger, and therefore internal parts are bigger than the 6.0L cousin injectors. Parts inside these are that much smaller that I don't think anyone would be able to see anything inside one of these visually, that would indicate sticking/weak performance. And if that isn't small enough, I can't imagine what the inside of a 6.4L injector looks like.
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