The real cause of injector failures?

[Black Dog]

Does anyone have any solid evidence of the real cause (causes?) of failures that some people have experienced?

I copied this from a post in the filter thread:

"Ask George about the pictures thru a elctron microscope of the inside of the injectors, he said it looked like the craters on the moon."

This, to me, sounds like a problem that is caused by cavitation, not wear from contaminants in the fuel.

If you are not familiar with it, cavitation is a phenomenon that occurs when a fluid goes through a large pressure drop. Air that is entrained in the fluid comes out of solution very quickly, and violently. This causes a huge release of energy that can easily erode steel. This is the same basic phenomenon that causes the coolant in a Powerstroke motor to eat through the block, except in that case the air is pulled out of solution by the shock wave caused by the combustion process.

I engineer hydraulic systems, and we see cavitation damage manifolds on a fairly regular basis. Steel will be eaten away just downstream of a large pressure drop, and the result looks like craters on the moon, just like what is described above. If the damage was caused by contaminants, you would expect to see sharp edges worn smooth, or bores enlarged with a smooth surface.

In our systems, the pressure drop is only maybe 5000 psi, and yet I have seen holes eaten through steel manifolds - you would not believe it could happen until you see it.

Certain customers seem to have more of this type of problems than others. It is not a fluid cleanliness issue, as we have done extensive fluid cleanliness testing with no correlation found between the fluid cleanliness and the occurance of this type of problem.

What we believe makes the problem worse in some cases is the chemistry of the fluid that is used. Our machines require a fire resistant hydraulic fluid, which is primarily stuff called water glycol it is similar to anti-freeze in a way, but it has additives for lubricity and stability at high pressures. There are a bunch of snake oil salesmen out there selling this type of fluid, and they keep the additive packages they use as trade secrets. We have had no luck in trying to pin this problem on a fluid vendor, as they all swear that their stuff is the best, but will not tell you exactly what is in it.

Anywhoo, if this occurs with a 5000 psi drop in our systems, I can only imagine the possibilities in a system with a pressure drop of over 20,000 psi. I could easily imagine some scenarios where adding extra filters, or using fuel additives could make the problem worse instead of better.

I would like to see some real evidence of what is causing the injector failures (I haven't had any problems), preferably from Bosch.

Food for thought.

[ 03-13-2003: Message edited by: Black Dog ]</p>

[jbplock]

Black Dog,

Very interesting points about cavitation. I believe www.preporator.com has a product that addresses entrained air in the fuel and resulting cavitation. Their website is currently "under construction" but they used to have a detailed description of their product posted there.

[dmaxalliTech]

Very interesting topic, but if it is cavitation, how would you stop or slow it down? I know that GM is aware of seat problems in injectors, and have since went to a harder( hardened) seat. still a little early to tell if that will cure the problem, but the cavitation thing sounds probable

[pinehill]

Well, I understand that Brokers got 480,000+ miles out of an '01 without replacing injectors. He did this with *three* fuel filters in series. Cavitation didn't seem to bother his injectors much. I'll be happy with half that many miles. smile.gif

[motovet]

Maybe a good fluoride additive is the answer. Seriously, this injector thing is making my head spin. I have read all the posts on this subject... think I want better filtration...use a fuel additive I thought was the best...have a new slight lope and am worried... hope GM got it right from the git go...and if not will stand behind their product. Man, all the money I spend on this truck should be enhancements, not band aids!

[george morrison]

As has been discussed, CAT did an extensive (expensive) research into the 'cause' of accelerated injector/pump wear. Dirt, simply, was the cause. Which moved CAT to adopt a 2 micron absolute fuel filter; which was quite a departure from the previous 20 micron nominal CAT had been using. Jet fuel is filtered to 1 micron. Now picture a CAT D10 bulldozer working in total dust and dirt: this bulldozer now has a 2 micron absolute fuel filter....
And yes, air is certainly a problem in high pressure systems and not to say that air may not be contributory here; we just *know* that dirt is a major cause from the tests that have been run..
George Morrison, STLE CLS

[roegs]

Pinehill...I would agree that BROKERS is probably doing something right to get that kind of mileage from his trucks. I've been looking all over trying to see what he uses for fuel filters. How did you know he uses 3 filters. Do you know what types?

[pinehill]

roegs,

A while back here, Brokers stated how his fuel systems were set up. He has a large, in-bed auxilliary fuel tank, and pumps fuel from that tank, through a filter, to the OE tank. He has also added another filter along the frame rails which is protected by a shield. So, those 2, plus the OE filter, make three. I don't recall that he provided the filter specifics.

[Inspector]

Blackdog:
Have you tried aircraft hyd fluid. We use Monsanto Skydrol 500. It is designed for high altitude low temp. It is also required to be non-flamable. It does require skydrol resistant seals. You don't want to get this stuff in your eyes. Our systems run at pressures of 2900 to 3200 psi. We don't have to many component problems. Hardly ever change a pump. Of course we are well filtered.
Denny

[george morrison]

Back to the water glycol. Water glycols have inherint pressure limitations. The problem is the water itself and that good 'ol Oxygen molecule. I have 6 inches of scar tissue myself from working with these hydraulic fluids and have seen many, many cases just as you describe. The release of the oxygen/air will suck the surface right off the piston/pump area..
In fact, this is exactly what is occurring in many of the Ford PDS cases. The fuel system is very prone to air leaks. This is the source of many an injector failure on the PSD engine; along with a fabled "cackle". There are folks at the PSD site who have installed clear fuel lines to try and pinpoint oxygen sources!!
So, yes, water and air can indeed be destrucitve. However, from the previously mentioned extensive research accomplished by CAT/SWRI, dirt was found to be the most significant in fuel systems that were tight, with minimal air/water contamination.

In straight hydraulic systems using oil, if in fact we have a cavitation issue, goodby pump in a heartbeat. The air molecule literally explodes on the release side of the high pressure (6,000 psi or more) and sucks the surface..

However, I can calculate servo valve life directly proportional to dirt levels/ISO cleanliness levels in a fluid. Which CAT in fact did in its research on dirt levels in fuel. If I reduce just one ISO grade dirt level, I will see servo valve life doubled...
Correspondingly, if we reduce our fuel dirt level from a 19/17/15, to a 15/13/10 level, in our 30,000 psi system, well, shall we say injector/pump life will be a non issue??
As can be seen with Brokers extraordinary injector/pump life..
George Morrison, STLE CLS

[ 03-14-2003: Message edited by: george morrison ]</p>

[VA_Dmax]

Maybe Im confused here but what does running a CAT in a dusty/dirty environment have to do with filtering your fuel. That would be the air filters job. Whether you run a vehicle in dust or particle-free air, the fuel filter doesnt do a thing different in either one. Or am I just ignorant here?

[george morrison]

I am not sure what post you are referring to with respect to the CAT and dirty environment. However, the environment does indeed play a part in this whole scheme of clean/dirty fuel. In the case of the CAT working in a harsh environment; diesel fuel is surface reactive. That is, if there is a high concentration of aiborne dust, diesel fuel will actively pull those particles into the fuel; as in a fuel storage tank located at a mine or construction site. None of these tanks are 'protected' from dust/dirt/moisture. Thus the fuel filtration system is going to be much more heavily taxed in those operating conditions; I have tested diesel fuels from construction/mines with ISO cleanliness (dirt levels!) of 26/24/22!
Hopefully this is the answer to your CAT question and its relevance to environmental conditions.
George Morrison, STLE CLS

[VA_Dmax]

Our trucks have a closed fuel system correct? So as long as we arent getting diesel from tanks exposed to dirty/dusty conditions, we dont have to worry about our fuel picking up dust out of the air right?

[george morrison]

My CAT reference was primarily relating to the difficulties fuel systems are dealt and the steps CAT has taken to minimize fuel system damage. As a result, we have benefited from CAT's extensive research into the cause of the early fuel injection systemfailures, high injector wear rates, fuel filter design, etc.
I apologize if I was unclear with my reference.
We get enough dirt in fuel through our normal fuel sources!
George Morrison, STLE CLS

[Amianthus]

My understanding of the nature of cavitation is that a liquid suddenly drops pressure to a pressure below the saturation temperature for that liquid at that temp. Therefore it starts to "boil" and flashes to a vapor. Then, since vapors are compressable, the vapor bubble is compressed causing collapse. This causes the shockwave that can pit the material. This whole cycle of expansion of fuel vapor and rapid collapse of the same, is what I know to be cavitation. Although air probably has something to do with the problem at hand, that's not cavitation as I understand it.

[roegs]

Pinehill...thanks for the note on BROKERS filters. Wish I could get the specifics on what he's using. I'm pretty impressed with the mileage he gets from his trucks.

[jbplock]

VA_Dmax,

The fuel cap on our trucks will vent "in" but not "out". So, as the injection pump pulls fuel out of the tank, outside air comes in through the cap. If there is dust & dirt in the air, it will also enter the tank.

And, as George pointed out...

" ... if there is a high concentration of aiborne dust, diesel fuel will actively pull those particles into the fuel"

smile.gif

[ 03-16-2003: Message edited by: jbplock ]</p>

[huntindog]

Sounds like we need a filtered fuel cap!

[a bear]

Bill, huntindog
I have a 2 micron tank vent with desiccant beads for absorbing moisture that I purchased from the AV Lube site to install for my fuel tank. It's about 3" x 3" in size. I had asked for comments on the DP as to the benefit but recieved 0 replies. Was going to use this in conjunction with a non vented cap and a small check to prevent outward venting. The vent sells for $24.
It's on the AV lube sight under aviation

Any replies would be appreciated

[jbplock]

Tommy,

Sounds like a neat idea... How do you plan to mount the vent on the tank and will the check valve go in series with the vent? The OEM cap will not vent "out" probably to meet EPA/emissions requirements (??).

[ 03-19-2003: Message edited by: jbplock ]</p>

[Dmaxenvy]

Does anyone have statistics on injector failures in the Dmax? Or know where to find these? With all the talk about these failures, it gets me to wondering what the incident rate actually is.

[ 03-21-2003: Message edited by: Dmaxenvy ]</p>

[permx11]

If a little air pocket can damage the injector, how about that little air causing the dreaded ticking noise that they say will not cause any damager.

[Lone Eagle]

a bear, I just read your question on desiccant beads. I worked with several types of desiccant that we used in our compressed air system, chemical tanks, AP containers etc. Disiccant will work to remove moisture in a sealed tank. Does yours have an indicator to tell when it is saturated? Any data on what type and how to reactivate it? All that I am aware of have to be heated to drive out the moisture.
This subject started off talking about cavitation. Absolutely not!
Later! Lone Eagle ;) ;)

[ 03-21-2003: Message edited by: Lone Eagle ]</p>

[a bear]

Bill, Lone Eagle,
Sorry I took so long to write back. Actually forgot about the post. I hadn't really thought about the install yet because I was kind of waiting for opinions to see if it was really worth while. The vent is a 2 micron with the desiccant beads that turn from light yellow to blue/green when saturated. I think the beads can be reactivated by placing in an oven for a while. Since I have a bag of this stuff I would probably just refill the canister. Was kind of thinking of this because my truck is often run in dusty conditions and sets a week at a time when I'm offshore.

The vent is at this site under aviation http://www.avlube.com/

[Lone Eagle]

a bear, I think it will be more trouble than it is worth. You must keep your spare desiccant in an air tight container. I have a couple 1/2 lb. bags of activated alumina I put in a sealed container with my reloading primers. The reactivation cycle for mine is 12 hours at 250 degrees. Your is going to smell like diesel. I don't think your wife is going to go for that in her oven. Later! Lone Eagle :D

[ 03-21-2003: Message edited by: Lone Eagle ]</p>

[a bear]

Lone Eagle,
I agree, It's probably just more trouble than benefit if any. Good fuel filter maintenance should be plenty enough. :D

[BlackMax]

Let me start by saying I do not know very much about diesel fuel but I sure like the truck I have that uses it for fuel. My question is wheather there could be anything in diesel such as impurities or just the make up of the fuel itself that can turn to a solid if compressed to 20,000#. I do know that this does hapen with other liquids. This is just question I had that I am sure some one on this site can answer for me. Thanks

[zip]

Blackmax- When diesel fuel is compressed, it causes heat, ie., in the cylinder of the engine.The result is an explosion which creates a gas and drives the piston down to turn the crankshaft. I sure hope it doesn't turn into a solid. Awful noisy going out those exhaust valves!
:D

[BlackMax]

I realize what happens in the combusten chamber but that is after the injecters. What I am concerned about is if there are any solids formed when our high pressure pump compresses the fuel before it reaches the injecters. The filter could be doing its job but if the solids form after the filter they will plug the injecters. There continues to be talk about solids in the common rails and I just wondered if it could be from compressing the fuel to the levels that are required in our engines. Like I said before this is just a queston and is probably way off base. But if you don't ask you will never get an answer.

[Lone Eagle]

Amianthus, Your definition of cavitation is real close. This problem in hydraulic systems is usally associated with the pump. I have not seen a drawling on our fuel system but I am real sure our pump does not make 30K PSI. It is made by a hydraulic intensifier in the injector. I know at least one guy on this forum that knows exactly how these injectors work. I wish he would draw us a picture. Later! Lone Eagle ;)

[Black Dog]

Lone Eagle, you are thinking of the HEUI system that International uses. On the Bosch injection system on a Dmax, the entire fuel rail is pressurized to 25,000 psi (give or take) by the pump.

[Lone Eagle]

Black Dog, I have worked on 10,000 PSI water knives, pumps and the piping systems and let me tell you they are heavy duty. My son is an ME that designs 30,000 PSI robotic water cutting machines. They acheive the pressure with intensifiers. Like I said, I sure would like to see a drawing. Later! Lone Eagle

[ 03-25-2003: Message edited by: Lone Eagle ]</p>

[TraceF]

jbplock-

&lt;&lt; The fuel cap on our trucks will vent "in" but not "out". So, as the injection pump pulls fuel out of the tank, outside air comes in through the cap. If there is dust & dirt in the air, it will also enter the tank. &gt;&gt;

Not entirely correct. There is a 3/8" filler vent hose that can take air either way.

[FirstDiesel]

You talking about the hose clipped next to the filler neck?? Isn't that the vent from the rear axle?

[TraceF]

I stand corrected FD. I only moved it 20 or 30 times while working on this project but never traced it beyond my reach.

[FirstDiesel]

I hear ya. Was wondering what it was when I was installing the fast fill neck and didn't see it going to the tank.