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Discussion Starter #1
Possible Post Warranty CR Fuel System Modifications.

Most of what I will talk about may void warranty (?) but my whole thrust will be to not do anything to cause any operation of the fuel system to change. I hope that what I do will not effect any certification, but I totally realize some may not think this is true. Go ahead and express your concerns and solutions to overcome the problem you have concerns about. We will see what changes I may need to make.

I am a tag along on the CR problems. Most of my involvement has been in the PD cam failure area. I do not own a CR but have a HPFP thanks to dweisel. My first area of interest is helping see that extra filteration is added to the CR system. Many have talked about filtration and it is time to try several ways to get this done. If you have ideas post here or start your own thread, but warranty end is approaching for a lot of cars. Since the CR fuel system failure is so expensive, there needs to be much work done in a hurry.

Some feel that filters will upset the whole system. Tests can be done to see what happens. Another boost pump can be added if needed. Anyone willing to take stock test pressure readings could help establish guidelines?

I got involved with the CR mostly through listening to dweisel. Since he had a failure on one of his CRs he has a personal interest. I do not own a CR but will help if I can. Before I buy a CR I want to have a filtering system worked out. I tend to make a list of all the problems and work on those I see as reasonable to fix. Since I do not own a CR take that into consideration. Right now there are about 10 areas that need to be addressed.

Any part or combination of the following:
The wear of the HPFP: roller and roller holder, slider piston and slider piston bore, cam, bearings, etc.
The wear material in the High Pressure: rail, injectors etc.
The wear materials in the return system:tank, lift pump

I want to look into:Filtering; bushing the pump housing (with possibly 426 hemi valve lifter repair bushing); possible whole new seperate oiling system for the HPFP (sump, pump, filter etc); a filter adapter to protect the High Pressure system (done at low pressure feed for HP side), a possible adapter for the pressure relief valve (to change flow path to help return fuel filtering); an adapter and new roller assembly for the HP pump; etc.


Most of the things I tend to do are out of the regular boxes folks work in. I am a shade tree mechanic. Just because something is not stock does not bother me. The stock stuff is failing anyway. I do try to keep emissions systems happy. It is just my nature to work with problems.

Wear materials are not filtered out of the CR system, but are spread throughout the whole system. At failure time the whole system if full of wear material and total system replacement is necessary. I want to find ways to trap the wear particles and just let a minimum amount of parts be replaced at failure time. These filters will not stop a failure but may contain the failure. Right now The problem is talked about elsewhere, but there is a great need for everyone to be involved.

My first thoughts were for drilling the HPFP housing, but an adapter or adapters are an optional way others have suggested to approach this. I have found a local person with a vertical milling machine who will allow me to use it. No telling how much work I will have to do to pay for its use. LOL.

I will be transfering some of my posts from the dweisel thread shortly. If you wish to discuss filtering I hope this is the spot. If someone else has a thread already, let me know. My search words did not turn it up.

eddif
 

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I usually never go back and edit my initial post. If a statement looks strange or mistaken PM me and I will give you any updates; or look for later posts that straighten out any mistakes in thoughts or new information.

eddif
 

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Discussion Starter #3
Fuel: Inter-heater / Heat exhanger / After-heater

Fuel: Inter-heater / Heat exhanger / After-heater

I have run up against a major conflict in adding filters. Nothing that can not be gotten around, but something that I need help on.

The problem: I think like a Gulf Coast Resident. I have never had diesel fuel wax plug a filter.

So​

I can add all sorts of filters where I live and never see a problem. Those filters that I can so easily add, can kill a cold area car in short order.

My first question is: Do micro-glass (?) filters plug the same as the traditional filters? The folks selling them imply that they do not, but I am risking cars on my thoughts and some hard fast official test results are needed.

Can anyone help?

A Possible Solution
This very thought is one of the reasons the CRs fail. IMHO Cold loop fuel (contaminated wear containing fuel) goes into the clean side of the filtering area to rapidly raise the temperature in the filter (to thaw / heat the filter and promote flow. IMHO Return fuel in the dirty side would take too long to thaw / heat the filter again in my humble opinion. A seperate heat exchange unit / inter-heater / after-heater would possibly solve the problem but would be a complex unit to work really well. An oil cooler has two fluids seperated but transfering heat. Too keep the wear material seperated from the clean fuel this is what we really need.

eddif
 

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Subscribing. I probably wont contribute much as I am on the steep curve of transition from a single wire old style diesel to this new system. I plan on keeping my TDI for a long time so any after market upgrades I can get will be well appreciated!
 

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Discussion Starter #5
Fuel: Inter-heater / Heat exhanger / After-heater

I have run up against a major conflict in adding filters. Nothing that can not be gotten around, but something that I need help on.

The problem: I think like a Gulf Coast Resident. I have never had diesel fuel wax plug a filter.

So​

I can add all sorts of filters where I live and never see a problem. Those filters that I can so easily add, can kill a cold area car in short order.

My first question is: Do micro-glass (?) filters plug the same as the traditional filters? The folks selling them imply that they do not, but I am risking cars on my thoughts and some hard fast official test results are needed.

Can anyone help?
Edit from Here down Retract My statements about the fuel loops for the 2 hole filter till I have more information.
A Possible Solution
This very thought is one of the reasons the CRs fail. IMHO Cold loop fuel (contaminated wear containing fuel) goes into the clean side of the filtering area to rapidly raise the temperature in the filter (to thaw / heat the filter and promote flow. IMHO Return fuel in the dirty side would take too long to thaw / heat the filter again in my humble opinion. A seperate heat exchange unit / inter-heater / after-heater would possibly solve the problem but would be a complex unit to work really well. An oil cooler has two fluids seperated but transfering heat. Too keep the wear material seperated from the clean fuel this is what we really need.

eddif
Please note that I have been informed that I may have made a mistake on understanding the 2 hole filter diagram. Till I know more, it is safer just to go back and say I am wrong. I will try and find out the truth and be more careful

Sorry

eddif
 

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The VW diagrams seem to show the return fuel entering the fuel filter on the supply (tank) side, so it wouldn't be contaminating filtered fuel. It would also retard waxing of the filter element if the flow is in that manner.

Any filter element can be clogged by waxing if the fuel is cold enough. Preventing waxing generally requires that the fuel be heated or treated to reduce the cloud point or #1 diesel/jet fuel be used instead. Treatment generally lowers the lubricity, #1 diesel was known to have reduced lubrication qualities in the high sulfer days. Engines built to run on jet fuel generally had specially made fuel pumps, one maker fitted their engines with arctic specification pumps (more wear resistant due to thinner fuels with less lubricity).

One issue I need to point out, is that I expect that if the VW fuel engineers who designed the HPFP thought they could oil lubricate it without possibly contaminating the fuel and wiping out the pollution control widgets (much $), they'd have done so. This is most probably a dead end.

I do believe that the wear particles are the result of lubrication failure, not necessarily a bad choice in materials. The question is if the failure is the result of bad/contaminated fuel or design issues or a combination thereof. And yes, failure to consider the effect of premature wear and take preemptive action is an engineering error, probably dictated by management/ego.

BTW, from the earlier thread, a 7 micron filter removes particulates as small as 0.00028 inches as near as I can calculate. Any physical chemists who may wish to further enlighten us as to exactly what their specialty may tell us in this matter are requested to speak up. I believe a filter between the transfer pump and HPFP supply side to be the easiest addition, although I believe a filter between the low and high pressure sides is a design necessity. I also believe it will be a nightmare to do (I was a machinist, however, I haven't actually seen a pump, just going by drawings.).

Anyone have any idea what the filtering capability (in microns) of the factory filter is?
 

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Discussion Starter #7
One issue I need to point out, is that I expect that if the VW fuel engineers who designed the HPFP thought they could oil lubricate it without possibly contaminating the fuel and wiping out the pollution control widgets (much $), they'd have done so. This is most probably a dead end.

I do believe that the wear particles are the result of lubrication failure, not necessarily a bad choice in materials. The question is if the failure is the result of bad/contaminated fuel or design issues or a combination thereof. And yes, failure to consider the effect of premature wear and take preemptive action is an engineering error, probably dictated by management/ego.

BTW, from the earlier thread, a 7 micron filter removes particulates as small as 0.00028 inches as near as I can calculate. Any physical chemists who may wish to further enlighten us as to exactly what their specialty may tell us in this matter are requested to speak up. I believe a filter between the transfer pump and HPFP supply side to be the easiest addition, although I believe a filter between the low and high pressure sides is a design necessity. I also believe it will be a nightmare to do (I was a machinist, however, I haven't actually seen a pump, just going by drawings.).

Anyone have any idea what the filtering capability (in microns) of the factory filter is?
Hopefully there are no errors:
I think the diameter of the roller chosen to move the High Pressure piston has too small a diameter to provide an adequate hydrodynamic film. I guess the lubrication term and hydrodynamic film term blend as we describe the possible wear. The exhaust treatment sure cuts down on some lubricants. O course I am no engineer, but the film thickness of diesel fuel on a small diameter roller is not that thick (especially where the roller meets the cam lobes). When you start discussing the size of wear particles found in the CR injection system, you are sure talking about a particle that the roller has to almost jump over, or have the particle partially mashed into the cam surface (?). If you have ever seen a worn cam lobe there is some serious wear. If there never was wear material, the system might work longer (with no gasoline miss-fueling). The only problem is the failures show there can be wear material. We really need some inspections before failure to see what is going on. A failure just starting can help identify wear just starting and where it is starting.

After you begin to read of industry filtering going to 2 microns and below, you can look at diameters and know why. A roller does not have a knife edge but the larger the roller the more effective surface area the hydrodynamic film acts on.
+++++++++++++++

A filter need (?) between the transfer pump and the HPFP, would depend on how much wear material the transfer / boost pump is making. Do some suggest we need a third added filter? Hey we are open to all suggestions. Because of the problems: Filtration, Filtration, Filtration.
+++++++++++++++

The added filter after the HPFP low side and before the High Pressure piston is just a pretty much given need. The machinist need is a consideration. The smallest piece of material needed is roughly about 2" / 54mm X 1 1/2" / 38mm X 1 3/4" / 44.45mm (L,W,H). In that you have to drill all sorts of holes and do a turning. I am going to cheat and cut out some lathe work, but the mounting of the electrical control valve will be a bit high. My design thought will be about 1 1/2" / 38mm higher than where it sits now. Banging the engine cover I am sure. Maybe after I make the first one I can see a way to do all this easier. A great machinist can cut the height down to about 1" / 25.4mm or possibly less. I am sure not great, or even fair so the need for an extra 1/2" / 13mm. The plus is the valve has about a 3/16 / 4.75mm maximum flow orifice. Hopefully 1/4" fuel line will work.
By the way:
The lower hole in the pump is almost exactly 5/8" x about .175" deep (the floor is not flat)
the larger hole is about 7/8" X about .380 deep (there is a bevel for seal installation to deal with etc.)
Together they are about .565" deep but these bevels make accurate measurements difficult.
These measurements do not add up. You have got to understand that you need bevel guages and just looking I know they are not 45 degrees. I may change some things about the measurements I finally use. We need a pump cut apart on a bandsaw to really show what is going on. Never give up the chance to collect used parts. Please send them to those you know will give information to the club.
+++++++++++++++++

The return needs a filter to keep the wear material out of the original filter and the fuel tank. We are talking a serious size 2 micron filter. No use to wimp on this filter, it needs to handle a lot of fuel. Since it flows about the same amount of fuel the original filter flows, it may need to be changed more often. I mean if the original filter is 5 microns then this 2 micron filter will see a lot of filtering going on. We can cut corners and try for 5 microns, but everything I read shows the need for 2 microns.

No use to cry over spilled milk, just get the mop out and clean up the CR mess.

eddif
 

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I believe the roller size is chosen to provide self alignment with the cam. Yeah, you can reduce loads by increasing the roller size, but then you have to provide cam alignment another way. Bosch went to flat tappets to eliminate cam following rollers in their MW/MEW series injector pumps a long time ago. Dunno about any differences in cam loading between the pump designs, but the earlier pumps were oil lubed.

I agree 2 micron filtering is indicated, but couldn't find units of proper size/pressure compatability.
 

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Discussion Starter #9
I believe the roller size is chosen to provide self alignment with the cam. Yeah, you can reduce loads by increasing the roller size, but then you have to provide cam alignment another way. Bosch went to flat tappets to eliminate cam following rollers in their MW/MEW series injector pumps a long time ago. Dunno about any differences in cam loading between the pump designs, but the earlier pumps were oil lubed.

I agree 2 micron filtering is indicated, but couldn't find units of proper size/pressure compatability.

You will have to explain the roller size alignment issue when we may be only talking about a 25% increase in roller diameter. The other factor in alignment is when the roller assembly is galling in the pump bore, the ability to self align appears to be almost over. Thus, if dweisel comes up with a good bore coating, the ability to slightly increase roller size may rapidly increase.

If the bore is bushed with a 426 hemi valve keway repair sleeve, the slotted keway type lifter can be used to self align the roller assemby.
http://jesel.com/index.php?categoryid=10

There is a size lifter that is almost our bore size.

eddif
 

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Discussion Starter #10
There is little wonder in my mind why that the HPFPs fail.

Just looking at this roller assembly you can see the design may have plenty of surface area to carry load in the coated pocket holder side, but little surface area where the roller contacts the HPFP cam. This works with no contaminated fuel, but is not robust enough to handle gasoline added to the diesel fuel. Even the coating wears away when gasoline is present. The 10mm roller will just not survive the gasoline mis-fueling.

If you go to the ZDDP Plus site and read the #11 hydrodynamic film article you will see the need for more surface area on the roller contact point.
http://www.zddplus.com/TechBrief11 - Internal Combustion Engine Lubrication.pdf

I am interested in seeing the different revised pump internals.

eddif
 

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