Let's talk injector life-cycle

[Rogan]

What is the 'average' life-cycle for an injector to operate properly? I realize there are hundreds of variables to take into account, but "on average", is it 100k mi? 120k? 150k?I'm starting this, due to the fact that I'm chasing down an issue with my truck, and ramhunter9 (Dave) and I spoke about this yesterday, for about 30 minutes or so.My truck has 180,000 on it, as of last weekend. I've been experiencing some mildly odd fuel issues, especially in the past six months. As you can see in my signature, I'm basically stock, with few minor mods:Edge Juice w/ Attitude + HotUnlockBoost Elbow5" exhaustBHAFFP is around 13-14psi WOT, 17-19psi no-loadRundown:I bought this truck about 2 yrs ago with 15x,xxx miles on it. When I first started driving it, the mileage was as follows:empty, 65-68mph, highway speed: 19-21mpgempty, under 50mph, city driving: 15-16mpgtowing, 60-65mph, 9000lb trailer: 14-15mpgtowing, under 50mph, city/rural: 13-14mpgoverall average miles per tank: 300-350Current scenario:empty, 65-68mph, highway speed: 15-17mpgempty, under 50mph, city driving: 12-14mpgtowing, 60-65mph, 9000lb trailer: 13-14mpgtowing, under 50mph, city/rural: 10-12mpgoverall average miles per tank: 260-290The fuel economy has been a semi-gradual decline over the past year. Fuel filters have been replaced, oil changed regularly, trans fluid/tcase/diff fluids changed. No binding or dragging of brakes, etc. Overall, everything seems normal or fine.cold startups in the morning yields a black puff of smoke, where it used to not do that.gear changes and initial accelerations in the next gear:Edge setting: 0: no smoke, maybe light haze1: same2: noticeable smoke3: very noticable4: trails smoke5: blacks out behind me6: insane 6% grade climb, 55-60mph, pulling trailer, 5th gear, ~20-24psi:2: light/noticeable smoke, EGT ~10003: noticable smoke, maybe little more than 2, EGT ~1000-11504: EGT > 1200, heavy smoke0, 1, 5, 6: Never pulled the grade in these settings.Dave and I think possibly I've got a bad/leaky/worn out injector, or multiples. I cannot reach anything above 30psi boost, and that's with the boost elbow completed closed, or very slightly open.I'm gonna freshen up my hx35w, and prepare and start collecting parts to go compound turbos, but in the meantime, I'm chasing this fuel economy decline, and such.

[Mopar1973Man]

I hate to say it but I've got CajFynn's old RV275's and they have over 400K miles on them. All Ive done is clean them up and re-installed. As you've seen from my other post my MPG's are good and high.I'll have to dig up a old post about using a digital calliper on them and measured all the parts for fit.I would look toward drag being more of a issue like your brake calliper etc.Possibly a VP44 getting weak in timing?

[Rogan]

Thoroughbred Diesel's "how-to" injector removal 24V

http-~~-//www.youtube.com/watch?v=Si8r9ZutrGo&feature=related

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sorry it's sideways, but whatever ...

look in the mirror at the below video. Setting on 4, 3rd gear, 35mph, from off-throttle, rolling on it smoothly to about 1/4 - 3/8 throttle. the first plume is acceleration.. then I let off (smoke stops) then instantly puffs out more black as decel starts..

http-~~-//www.youtube.com/watch?v=P-B2hPwyw7U&feature=plcp

[Haggar]

Interesting.The GM 6.5 respond well to new injectors, and seem to last only about 100k. Those injectors are no where near as heavy as the Cummins appear to be though. So its interesting. I would think that you would have these injectors tested at some mileage point. (but replacement cost does not seem to warrant testing, just replace them. I was surprised how inexpensive they seem compared to the GM ones.) Not sure who is testing them, but I am certain someone does. Pop pressure and pattern are important. Could time of year have anything to do with your mileage? (like one year all your driving was in the summer, with the better blends and one year more driving with the poor winter blends.) IMHO it would be 1)injectors 2) timing issues (which could be injector related or VP) 3) driving "styles" (actual style, drag, tires, change in scenery etc) 4) fuel blend 5) actual compression (whether from timing overlap of valves, or rings) (just saw the video) With your smoke, I would test the injectors. That one burst of smoke was more than my truck smoked total pulling the tractor Saturday between farms.Hag

[hex0rz]

I don't think you mentioned whether or not you had turned off the Edge Chip and tested to see what results came from that. Its hard to say whats going on unless you turn the chip off.I say this because, if you look at my signature, I have 70hp DAP injectors. On a WOT pull, I may get a haze. So, being that you have stock injectors, it makes no sense that your smoking that much.Another good way to tell if your injectors are going out is to check your oil. I know when my injectors were going out, my oil was constantly venting. Diesel was being added to the crankcase and washing it all out. At the time I was also just around 200k miles.When I replaced my injectors, the oil vented out for a while then stopped quit a bit. I checked the dipstick, and the level was from way over the top of the full mark, to at the half-way point between the marks.Also, take the dipstick, get a good amount of oil on it, and take a papertowl and let the oil off of the dipstick drip onto the papertowel to create about a dime size blob. Watch to see how big it grows and if the growth is a pale color. You will see what is oil and what is diesel. I think from a dime size to a quarter size, you have leaking injectors.Hope that helps...

[CSM]

I am not an expert, but I would venture to say that wear and tear on injectors is cumulative.

If the truck is ran well, on long hauls and kept within operating temps for long periods with clean fuel, the injectors will have near as makes no difference infinite life span.

The springs should be designed for infinite life.

The bodies themselves have very little stress.

The needles and seats are what will wear out eventually. Wear surfaces cannot be designed for infinite life unfortunately... but in the case of these injectors the surfaces are quite well mated to each other and should last a long time.

If there is a lot of carbon in the motor, and there is a lot of water or foreign debris in the injector the injector needle and seat surfaces can be damaged on a microscopic level, and any wear will increase the wear rate of the mating part.

I was told by my old Cummins tech that the 1st and 2nd gen poppet style injectors were designed to "break up" and push foreign objects through up to a certain size, but once that debris wears your needle/seat to the point where your injector leaks your timing on that cylinder will be off and you will likely have problems with the engine missing and possibly burning a piston/exhaust valve.

2 stroke oil isn't a fix all, but it certainly doesn't hurt the injectors. The best thing I can gather that helps injectors in all engines is clean fuel and allowing the mixture to be such that the temps are nice and warm, but not super smoky. And if you do get sooty and smoky, be sure to get the EGT temps up to normal operating and cruise that way once in a while to burn off the excess carbon. Not only would this help injectors, but it will clean out the exhaust side of the turbo, valves and manifold with an lean, hot, oxygen heavy mixture.

CajFlynn, our resident marathoner is a good example of clean burning, and though I can't say that his success is definitively due to his driving practices, our engines do like being up to temp and to be put under a "normal" load for long hauls rather than to be used to race, pushed too hard, or pushed too little in a 1-2 mile drive daily. I've read that the ISB was originally designed as a generator power supply, and I can say from experience with Cummins genset engines that they will go from cold to 2200 RPM and stay there for decades as long as they are kept away from ether, fed good fuel, and they are even surprisingly resilient to infrequent oil changes compared to some of the Caterpillar motors we see at work.

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Also, here is some other extraneous info that I recall in case somebody is interested. Gas engines are designed to be run a little bit rich, a wee bit more fuel than air, since spark ignition requires a near ideal mixture to ignite. In theory, you have to meter both the fuel and the air going into a gas engine.

In diesels, they were designed to be run lean, as in more air than fuel. Diesels will run with just about any mixture of fuel/air and they are throttled by metering the fuel only... Think about it, you have no butterfly valve in the intake of the diesel like you do with gas. The engine (if intake,turbo,etc. are adequate for the chip,injectors etc.) will suck as much air as it needs to run. It will still run when over fueled, but it will be less efficient and create a lot of soot and heat. This heat in the exhaust is what spins your turbo. The hotter the exhaust temp, the higher pressure there will be in the gases going through the turbo, which will spin the turbo faster. Thus, the faster it spins, the more air gets pushed into the intake, thus lowering the EGT once the turbo spools.

The only real downside to diesels, is that when you run an engine lean of peak, is that it creates NOx pollution, the root cause of acid rain. NOx is what EGR combats, as if you run the NOx back through the engine, you can reduce the overall emissions... I am not an "environmentalist..." just sharing what I was taught.

[CUMMINSDIESELPWR]

Rogan,I recently had the same findings as you with my rig. It was upwards of 175,XXX miles and the stock original injectors were noisy as hell, i could hear a couple hitting a bit harder then the rest (injector knock) and i started seeing black smoke here and there when i shouldnt see any (leaking injector) My economy went down, efficiency went down, response went down, just basically heading south overall.i wasnt able to hit over say 24 psi on the turbo with the worn injectors either, with the new ones i can hit 29 easily on setting 5 if the clutch will hold... but the turbo is very worn and a rebuild is in order.When i replaced them it all went away. and the truck drives so much quieter and more responsive, in fact i have to relearn how to drive it as i was taking it easy with worn injectors and i need to drive it like its fine and no issues. I do however need to rebuild the worn turbo and replace the stock clutch, as anything over stock setting spins the clutch....

[Rogan]

you know, Randy... now that you mention the injector "knock"... I've noticed a lot more noise under the hood.. tapping, if you will.. I suspected valve lash, and planned on adjusting them this weekend.. But what you explain is EXACTLY (as a whole) what I am now experiencing... Thanks, I'll definitely press forward on getting some injectors now, first.

[Haggar]

Still thinking on this..... Might call the cummins shop guys and look for their input. (did some quick searches and found no "established interval" of inspection.

"Infinite life" is usually expressed in design as a component that doesn't fail at less than 10⁶ to 10⁸cycles. We frequently use 10⁷ cycles. (it is used for fatigue life calculations)(there are a whole SLEW of other design considerations too...)(springs can be very finicky mechanical components...)

If our engines run at 2000rpm, (that is crank shaft revolutions.... the intake event only happens once every two crankshaft revolutions) a single injector operates at 1000cycles per minute, or 60,000 cycles per hour. So depending on design criteria, the "infinite life" mile stone was passed at 16.7 hours of operation (10⁶ cycles) 166.7 hours (10⁷ cycles) or 1666.7 hours (10⁸ cycles).

If we figured 55 mph at 2,000 rpm (I have no clue if that is reasonable, have not owned mine long enough) at 1666.7 hours of operation, that is about 91 to 92,000 miles.

Back to the infinite life..... Notice it says "does not fail". Fail in engineering terms usually means break. What happens to the actual spring pressure? The spring has had to have had some plastic deformation, so its holding ability has changed. Thermal cycling has changed its hardness. If you go back in time to our old gassers, do you remember floating the valves? As the engine got older, the ability of the valve spring to keep the lifter following the cam degraded. The spring got weaker over time. (thermal cycling and use). We used to shim the springs to get the closure pressure back in specification, which kept the valves from "floating" during normal operational frequencies.

I have not gotten into the wear aspect of the nozzle. These injectors (and IP) were designed in the time before LSD and ULSD. In the act of removing the sulfur, lubricity was changed (lowered). Wear extent and patterns are different that during the design process.

So, sorry for the book, but I think I am going to have my injectors at least looked at every 100k or so, until I can find more information.

Hag

[CUMMINSDIESELPWR]

well look also with the nozzle, you have a mated surface hammering on another mated surface with a specific spring pressure millions of time through its life, it will wear and crack or break.my engine would have good days and bad days concerning noise from the injectors, when you got on the gas it was noisy but when you let off and coasted still in gear the noise all went away and valve train was quiet. this pointed directly at injector noise to me.