Dial type torque wrench, sorry I'm dense

[Rawze]

(01-29-2017 )Starlight Wrote:  Torque the injectors down to 82 in lbs. You will notice a difference in how it runs. It will also save you from having a leaking injector caused by it having low preload if your top end service is prolonged. So if you set it to 82 in lbs and they loosen off a bit over time then chances are you will still be at or over the 71 in lb spec. I have had very good success with this method. I have had engines come in for service and the injector preloads were in the 50's. 2 of them were leaking as the low preload allowed combustion pressure to carbon up the pintle inside and fail the test.

No disrespect but I think you may not be aware of the consequences of what was suggested when altering this torque value by very much.

I have to disagree with increasing torque value by very much above the factory spec of the injectors while performing overhead adjustments for the reasons stated. Not even for preventing leakage, etc.

If the overhead adjustment is getting too far off over time and causing injector leakage, then I suggest it simply be adjusted more often. I always recommend adjusting the overhead valves and injectors every 200k - 250k miles vs every 500k miles for the prevention of possible problems just like that, and to keep fuel mileage at its peak. I would tend to think this a much better solution.

Problems created and/or introduced if someone increases torque on the injectors by very much ...

By increasing the torque, it increases the stress of the injector needle tip at its "crush-point", perhaps by quite a lot after the metering and timing fuel has been dumped away when it bottoms out. This can cause possible problems with not only the injectors themselves over time, but can also eventually cause injector cup or other head issues as the engine runs hot. As well, there is extra stress on the injector cam, rollers, bearings, set screw(s), etc. - The "crush-point" of the injector is all metal to metal when it happens, there is really no cushion when it completely bottoms out. There is also the possibility of deforming the injector or its lower plunger, weakening it.

(speculation): Increasing torque at the set-point will also alter the oil flow between the rocker and top of the injector plunger. Might lead to accelerated plunger wear?

My thoughts on the suggestion of improvements you have stated just simply are not worth the long term consequences by setting torque at a higher set point by very much. -- Leaky injectors SHOULD BE CORRECTED OR REPLACED, and setting things incorrectly to mask them is NOT a solution. The injectors should not "loosen up" in a short period of time. If they have, you have much bigger injector problems, someone has not properly torqued the set screws, or someone has oil flow issues causing accelerated wear.

I have seen and helped plenty of people set them to factory spec and have not seen where they "loosen up" and get leaky again after a short period of time/miles.

On the flip side, under-torqued injectors are another issue. I can easily see where the possibility of carbon packing in the pintle can happen by under-torqued injectors, but I would think it would also effect injector tip wear. Maybe even injector tip clogging as well. I have seen a few of engines where the injectors were actually set to 0 ft-lbs of torque for long periods that were actually much not leaky at all, but did have bad spray patterns, engine ran like crap. The metering check valve inside the base of the injector simply was holding back combustion gasses, that is its job on a healthy injector.

I have seen injectors set to 0 mistakenly because older mechanics will set them to 0 when doing overhead adjustments because they mistakenly think the injectors work the same as they do on older, or other model engines. It also retards the crap out of the timing and the engine efficiency suffers. I would be more inclined to think that the tip could become clogged or get worn/damaged easily by leaky combustion gas if it is greatly under-torqued. Maybe cause an increase of carbon/soot buildup in the fuel system if the check-valve in the injector starts to leak combustion gasses and the tip is not in the crush position. After-all, if the lower plunger is not seated all the way, it easily opens a pathway to the fuel return lines as the check valve in the injector gets dirty or weak.

Even so, it is the metering ckeck valve in the base of the injector itself that has to suffer clogging and failure to cause significant injector leakage at the metering solenoid, not the fact that it is possibly not fully seated. This points more towards fuel contaminants rather than a bit less torque on the set screw.

Just some explanation here...

On the ISX CM870/871, the injectors are held tightly in a DOWNWARDS position and are under the pre-set tension that was set by the dial wrench. Everything mechanically is bound up and pintle pressed tightly against the inside of the injector tip to keep the combustion pressure from entering. The injector tip during the entire combustion process is in this lower "crush position" until the end of the exhaust stroke. It is not until they approach roughly 45 degrees or more of the induction stroke (as fresh air is going into the cylinder) when they are released and would be more susceptible to any contamination. Excessive sooty EGR gas could lead to injectors getting dirty more often than they should.

The ring valve being worn out will cause accelerated wear to the lower plunger too, so I would tend to think that if an injector is old and leaky to the point of replacing, it would be better to do so as the best option. No amount of tweaking of the top of the injector to tighten the up above recommendations by very much is going to magically a worn out tip or leaky internal check valves, etc.

i have seen people take apart the injectors and clean the end of the injector plunger, its metering check valve, etc. and it reduce leakage sometimes. The problem will come back sooner than normal unless other components are re-worked as well though. It makes me wonder what injector re-man shops do about the ring valve and its replacement, etc., or if they even address it at all.

Your statement also warrants that an engine running a much cleaner combustion process would have much less overall injector/carbon leakage issues,.. and this is simply NOT the case so much. Leaky injectors seem to be more an issue of wearing components and reflected heat more than anything, but maybe one goes hand in hand with the other?.


- I can tell you for sure that people who drive around on blocked up exhaust systems and failing DPF cans will kill their injectors pretty fast. The result is VERY leaky injectors in short order almost every time. This is most likely due to reflected heat and pressure that cannot escape the cylinders properly because of poor exhaust flow most of all, further increasing soot and other troubles exponentially. Because of this, I think there may be merit to what you have stated about the relationship between the pre-load on the injectors and possible leakage issues, but the solution would be to fix the problems most of all, and not try to mask leaky injectors. Otherwise, there will be people trying to tighten their set-points every time they have a fuel issue, and that can't be good.

I have seen plenty of engines both with and without egr and emissions components in place with a LOT of miles (many with 700k+ miles or more) on their original injectors with no injector leak issues and serious neglect of proper overhead settings. I think that you may have overlooked that it could also be something besides carbon buildup is experienced and is seen in the fuel side of them. The ISX is notorious for asphaltene buildup due to bio-fuels. Combine this with the high heat they are exposed to and suffer, this easily leads directly back to the clear observations of leaky and ruined injectors from people driving around with blocked up exhausts. Perhaps the ring valve and check valve suffers the excess head damage?, leading excess wear, clogging, and the plunger not staying seated?- leading to the problems you are describing?. I would think fuel containment combined with heat would be a big contributing issue as well.

The twin-cam ISX models are well known to have accelerated asphaltene problems compared to other engines, mostly blamed for how the fuel is being trapped in the timing circuits, etc. Its buildup in the tanks and fuel system gets out of hand fast if not kept in check and is a common problem on them. - Most mechanics also mistake this as combustion gases and carbon getting into the fuel to boot because they simply do not know how the ISX and its fuel system works very well, or the effects of biodiesel on them.

I would think that these would be much better solutions towards preventing leaky injectors...

* keeping asphaltene at bay through better filtration

* keeping the exhaust and emissions components in better condition to reduce reflected heat as much as possible

*Preventing too much EGR gas and soot intrusion from entering the intake by ensuring you have good sensor feedback from the EGR and engine sensors.

* Preventing excess heat in the cylinders themselves if someone has custom programmed an engine through proper timing and maintaining Fuel-Air-Mixtures correctly.

* Ensuring the overhead valve adjustment is done before the injectors get too far out of adjustment and allow the introduction of the things like has been stated.

- If the goal that you think is to ensure more than 50-in-lbs of torque is always on them for the prevention of the things mentioned, then I would suggest tracking the amount of engine hours and/or miles an engine has on it in between setting them correctly, and the point where is has been reduced to 50-in-lbs from wear. Then perhaps a recommendation is in order on how often they should be reset accordingly, rather than trying simply increase toque with a blind settingthat could throw off timing and increase stress crush-points. Just my own thoughts on it anyways.
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Back to the subject of asphaltene ...

Leaky injectors will definitely cause soot and carbon to get into the fuel. You should check for leaky injectors if you suspect this, but the process is typically very slow and over a long period of time. If you don't have leaky injectors and want to control asphaltene problems, well this is what I do..

To control asphaltene in my own truck, I filter my fuel to BELOW 10 microns at all times simply by using better filters. I can tell you without question this is a problem with the ISX because I see it over and over even in my own truck. B20 fuel will clog those filters in only a few days with totally black carbon-looking gunk that most mechanics would accuse of being carbon and buildup from combustion getting into the fuel because they simply do not know better. B10 fuel does not do this nearly as bad where the filter will stay clean for a month or more instead. - I have had this buildup in my fuel system tested on my own truck trying to understand this process and without question it was asphaltene in the filters and not carbon/soot.

I found it very interesting what you have learned about these injectors and the causes of them to become leaky, etc. And I think you have some good observations on them. I had to take a very close look into the process and it shed some light on other possibilities. Here are a couple...

* perhaps NOT performing an injector leak test until someone has adjusted the overhead of the engine properly? - This could lead to a false positive? -- but then again,.. the check-valve should not be leaky, so this should have little to no merit?. - I would think the latter.

* Someone complaining about too much air in the return fuel lines when troubleshooting fuel system problems>? -- Perhaps an injector leak test is in order for that.

* An injector leak is not nearly as accurate as it can be. it can easily MISS revealing an injector that is actually leaking, but the check-valve has not failed, or is not leaky yet. - Maybe also check for pressure/bubbles in the fuel return lines as part of this test?

If someone's final goal is to tighten the "crush point" for reduced leakage on worn injectors, then I would suggest finding out why the injector is leaky to begin with. That means the check-valve is failing as well. Trying to mask it by tightening the set-point is not going to make this go away.

That is just my own thoughts on it all -- Rawze