CR engine HPFP analysis

specsalot · Apr 11, 2012

specsalot said:
Thats kind of what I was thinking. This suggests that by the time metal starts making it out of the pump that things are probably pretty bad inside. When you look at the flow pathway's in the pump, there really isn't a lot of circulation through the pump itself. One hole dumps fuel into the LP cavity. Another hole basically delivers fuel out to the Fuel Metering valve.

The predominant recirc takes place directly with the incoming fuel pushing past the overflow valve. I believe this pump is basically a dead end for swarf that goes round and round until there is lots of it. I'm sure there's a lot of fuel movement within the LP body, but nothing I can really see that would tend to move it out of the body.

The only other recirculation paths involve passage through the CR rail and either back through the Pressure Regulator or through injector leak off. I want to believe that any contamination making it to the CR rail would pose a major threat to the injection equipment. My conclusion is that very little contamination gets out of the pump via the HP side.

I've realized that I've fundamentally miss-stated things in the middle paragraph above. This is the risk of commenting without having hands on the parts as I write. I found a description I wrote some time ago that reminded me of what is happening.

740GLE said:
So what's peoples thought of a nice long high flow pull at say 3-4K for a few miles to flush out the HPFP? more harm than good?

The fuel flow enters the LP cavity of the pump through one hole which communicates with the inlet hose barb. Fuel exits the through another hole in the LP casing. This exit hole communicates with an exit pocket. A drilled passage from this pocket supplies the Fuel Metering Valve through an internal drilled passage. This exit pocket also communicates with the Overflow Valve. This valve sets the supply pressure to the Fuel Metering Valve by bleeding off excess pressure to the return system. This passage through the Overflow Valve is the primary recirculation path. Bosch places a screen on the inlet to the Overflow valve (to protect it from debris). This can be seen in the picture below:

So basically any large wear particles remain trapped in the pump by the screen on the inlet of the Overflow Valve. So to answer your question. The amount of debris that can recirculate back to the fuel tank is a function of the size of the debris and the condition of the filter screen on the inlet to your Overflow Valve. I recognize this explanation is clear as mud - but thats where we are right now scrounging around in the mud for answers. Sometimes all you can do is restate the obvious and hope insights follow.

The fact that outflow through the Overflow Valve has to pass through a screen is probably why I found wear material inside the HPFP. But I really didn't find much of any on the screen it's self. So even this basic idea that wear material becomes trapped in the pump has limited credibility based on parts I've looked at.

We do know from 2micron's measurements that the entire fuel tank contents likely pass through the HPFP is ~ 20 minutes time. Let's hope that trash that makes it in has at least as good a chance to make it out. The fuel filter does the bulk of work keeping fuel tank trash out of the inside of the HPFP.

The open question is how wear materials created within the pump make their way out.

specsalot · Apr 11, 2012

In the MY2012 Passat, VW has simplified the return path from the HPFP to the fuel tank. VW eliminated the fuel preheating valve contained in the fuel filter housing. In doing so, they eliminated the path that dumps HPFP return flow to the clean side of the filter.

2micron · Apr 11, 2012

Ebay Pump

Hello All,
specsalot, dweisel and many others have studied and commented on these pumps, which is very valuable information to all of us. Kudos to all that have taken an interest.
We are all learning from each others experience and differences in opinions. This is great!!!
I recently purchased a failed pump from Ebay for analysis and study. The pump was built in June 2009. I just opened it up and have had a short time to study it. The following photos are not intended to frighten anyone or show that the sky is falling. The photos are simply for reference and the people interested will certainly enjoy.
I have no history on this pump. For all we know, it may have run with gas or water in it.

.

.
The piston has clearly turned 90 degrees. A close look at the cam shows skidding of the roller, long before it turned. It probably only ran for minutes after it turned.
The diamond coating on the roller keep is in perfect condition, except an area in the middle. The aluminum bore is damaged, but surprisingly in good shape.
The pump is full of metallic (magnetic) swarf, in both the high and low pressure sides. The shaft bushings are completely destroyed as well. The amount of swarf in the high pressure side is less, but what is there is quite large in size.

.

.
The damage to this pump is severe. Please don't think your pump looks like this!! Again, I have no history on it.
In about a week I will have 2 more failed pumps, complete with rails, lines and injectors. More valuable is that I have a brief history on how they failed.
I will update with findings of contamination in the rails and injectors. dweisel has inspected rails and injectors in previous posts, and indicated contamination.
.
specsalot and others have been curious about what has been captured in the Return Line Filter setup on my car.
After draining the return filter into a cup, small metallic particles are always visible. These have been trapped and not allowed to return to the tank or clean side of the filter when cold.
I have been experimenting with the Temperature circuit bypass with success and will post details after more tests.
I have also filtered the 62psi Auxiliary pump output, before it enters the HPFP -But that is another post!!
All the Best,

specsalot · Apr 11, 2012

Some posters have a clear picture of flows. Here's a photoshopped picture to help illustrate the flow paths in this pump for the rest of us.

Supply fuel from the Aux Fuel Pump enters the LP body section of the pump.

Both Combustion and Recir Fuel exits the LP body section.

Combustion Fuel is passes through a drilled passage to the Fuel Metering Valve.

Recirc fuel passes through the Overflow Valve and exits the fuel pump

specsalot · Apr 11, 2012

2micron -

Great Pic's. Loss of parallelism between the cam surface and the follower will cause rollover rotation. Once the roller rotates 90 deg, there are no significant forces to bring it back. Bearing failure would probably alter cam parallelism straight away. The shaft journals went trough a world of hurt - lots of heat discoloration. My bet would be that the cam started skipping a bit when the follower bore became damaged. If I were betting, I'd say this was a severe miss-fuel event. Looks like it ran until there was little or no effective stroke left on the HP piston (like BrokenTDI's pump). This suggests the HP side and the CR Rail survived the swarf. Of course all this is pure speculation. I'll bet this is a low hour failure. The external surface of the HP section looks pristine.

dwiesel has probably inspected the most failed hardware and probably has the best feel for failure modes in these pumps. I'm pretty much in agreement with him that the issues between the follower / LP pump bore are where it all starts. 90 Deg rotation of the follower is probably where it all ends.

Great info - Thanks for posting

specsalot · Apr 12, 2012

Here's a pic (sorry about focus) showing the internals of the LP casing. I've labeled where the fuel enters and exits the LP casing. Fuel from the supply barb enters the casing at ~ 9 o'clock position. Fuel exits at ~ 11 o'clock. It is fair to assume that fuel moves around quite a bit in the LP casing under the action of both the rotating cam and the reciprocating cam follower. Circulation patterns of metallic swarf is anyone's guess at this point. For swarf to make it out of this pump, it must pass through the protective screens on either the Fuel Metering Valve or the Overflow Valve. If I have my sense of direction correct, the camshaft would be rotating in a clockwise direction facing the pump as shown in this photograph.

eddif · Apr 12, 2012

specsalot said:
I've realized that I've fundamentally miss-stated things in the middle paragraph above. This is the risk of commenting without having hands on the parts as I write. I found a description I wrote some time ago that reminded me of what is happening.

The fuel flow enters the LP cavity of the pump through one hole which communicates with the inlet hose barb. Fuel exits the through another hole in the LP casing. This exit hole communicates with an exit pocket. A drilled passage from this pocket supplies the Fuel Metering Valve through an internal drilled passage. This exit pocket also communicates with the Overflow Valve. This valve sets the supply pressure to the Fuel Metering Valve by bleeding off excess pressure to the return system. This passage through the Overflow Valve is the primary recirculation path. Bosch places a screen on the inlet to the Overflow valve (to protect it from debris). This can be seen in the picture below:

So basically any large wear particles remain trapped in the pump by the screen on the inlet of the Overflow Valve. So to answer your question. The amount of debris that can recirculate back to the fuel tank is a function of the size of the debris and the condition of the filter screen on the inlet to your Overflow Valve. I recognize this explanation is clear as mud - but thats where we are right now scrounging around in the mud for answers. Sometimes all you can do is restate the obvious and hope insights follow.

The fact that outflow through the Overflow Valve has to pass through a screen is probably why I found wear material inside the HPFP. But I really didn't find much of any on the screen it's self. So even this basic idea that wear material becomes trapped in the pump has limited credibility based on parts I've looked at.

We do know from 2micron's measurements that the entire fuel tank contents likely pass through the HPFP is ~ 20 minutes time. Let's hope that trash that makes it in has at least as good a chance to make it out. The fuel filter does the bulk of work keeping fuel tank trash out of the inside of the HPFP.

The open question is how wear materials created within the pump make their way out.

The screen on the photo is the pea sized screen I have mentioned so many times. When this screen stops up flow through the HPFP: decreases, pressure in the HPFP increases to booster pump pressure, more trash goes to the HP piston, etc.

When the valve is moved from the HPFP, an added filter placed filrering the output of the HPFP (with the valve moved to the other side of the added filter), and an adapter putting the filtered fuel into the HP piston (doing away with the normal dirty supply to the quantity control valve); things look better as far as filtering goes. This was discussed with flow diagrams way back.

If failures go up this summer we will be seeing the proposed added filtering looked at again. Some are now out of warranty and the need for collection of wear materials to prevent full system failure will be looked at with new vigor.

Adding filters that back up the standard filtering may help, but system help will only come with post HPFP filtering.

It does appear the Passat system is still working.

eddif

specsalot · Apr 12, 2012

The parts shown by 2micron tell an interesting story. 2micron has done some great work with supplemental filtration both from an installation and data perspective. His finding that metallic swarf continues to be found in the return line from the pump is eye opening. I'm at 15k and will be checking my filter before taking the car to the dealer for servicing (20k)

Softrockrenegade · Apr 12, 2012

Can it be checked and closed back up without new gaskets ? I'm close to 20k and would like to do this as well !

scdevon · Apr 12, 2012

When the piston loses its clockwise / counterclockwise orientation in the pump bore, it's game over.
I agree with those who say that the first place the pumps start to fail is in the piston to bore area. A partial piston to bore seizure occurs resulting in loss of orientation between the roller and cam lobe. The roller then has to ride on 1/10th (or less) of the cam lobe surface area it was designed to run on. A hot spot occurs almost immediately and smokes the cam lobe and roller because the roller slides instead of rolling (obviously)

That pump had gasoline or water ran through it, though. There is a hideous amount of wear on the shaft and the pump bushings.

specsalot · Apr 12, 2012

I think if you work carefully there should be no issue. Be sure to find one of the how to's posted out on the web. Most seals (I think) are formed o-rings. Just have to be sure they are where they need to be. There are threads in these forums and elsewhere that detail the process. I will be getting a book soon to insure I'm following the proper procedure. Key is to purge the housings using VCDS when done. Some will debate this aspect. I've worked on diesel fuel systems for years - air is a big no no.

diesaroo · Apr 15, 2012

specsalot said:
I think if you work carefully there should be no issue. Be sure to find one of the how to's posted out on the web. Most seals (I think) are formed o-rings. Just have to be sure they are where they need to be. There are threads in these forums and elsewhere that detail the process. I will be getting a book soon to insure I'm following the proper procedure. Key is to purge the housings using VCDS when done. Some will debate this aspect. I've worked on diesel fuel systems for years - air is a big no no.

I haven't researched the threads on the fuel filter procedure, but on my filter cannister, there seems to be a blue wax "tell-tale" on one of the cannister bolts. If it is there for that purpose, I would be worried that if it has been disturbed before the 20k mile service, then VW would have something on you, i.e. that you had tampered with it.

40X40 · Apr 15, 2012

diesaroo said:
I haven't researched the threads on the fuel filter procedure, but on my filter cannister, there seems to be a blue wax "tell-tale" on one of the cannister bolts. If it is there for that purpose, I would be worried that if it has been disturbed before the 20k mile service, then VW would have something on you, i.e. that you had tampered with it.

Drive more, worry naught about VW coming to your house in the middle of the night.

PS, They DO know where you live.....

Bill

specsalot · Apr 15, 2012

diesaroo said:
I haven't researched the threads on the fuel filter procedure, but on my filter cannister, there seems to be a blue wax "tell-tale" on one of the cannister bolts. If it is there for that purpose, I would be worried that if it has been disturbed before the 20k mile service, then VW would have something on you, i.e. that you had tampered with it.

40X40 said:
Drive more, worry naught about VW coming to your house in the middle of the night.
PS, They DO know where you live.....
Bill

LOL - Annocdotally VW's arbitrary approach to warranty of fuel system issues has us all wondering. When I had my recent issue (flashing glow plug) I walked in with my VCDS printout. Service writer was only concerned if I cleared the codes. We discussed the issue and his response was that, "It sounds like you are on top of it." My reply, "Thats what I will be paying you guys for."

I'd love to lever that POS anti-tamper plastic cap off my HPFP so I could inspect the follower assembly. Still haven't figured the magic to make it look untampered with. Dweisel says they never fit as well after being removed. Anti-tamper my axx. Tells me VW/Bosch knows this HPFP was junk from the get go.

EDIT: There's no anti-tamper crap on the Bosch CP3.x hpfp on my Jeep.

Niner · Apr 18, 2012

2micron said:
Hello All,
specsalot, dweisel and many others have studied and commented on these pumps, which is very valuable information to all of us. Kudos to all that have taken an interest.
We are all learning from each others experience and differences in opinions. This is great!!!
I recently purchased a failed pump from Ebay for analysis and study. The pump was built in June 2009. I just opened it up and have had a short time to study it. The following photos are not intended to frighten anyone or show that the sky is falling. The photos are simply for reference and the people interested will certainly enjoy.
I have no history on this pump. For all we know, it may have run with gas or water in it.

.

.

.

.
The piston has clearly turned 90 degrees. A close look at the cam shows skidding of the roller, long before it turned. It probably only ran for minutes after it turned.
The diamond coating on the roller keep is in perfect condition, except an area in the middle. The aluminum bore is damaged, but surprisingly in good shape.
The pump is full of metallic (magnetic) swarf, in both the high and low pressure sides. The shaft bushings are completely destroyed as well. The amount of swarf in the high pressure side is less, but what is there is quite large in size.

.

.

.
The damage to this pump is severe. Please don't think your pump looks like this!! Again, I have no history on it.
In about a week I will have 2 more failed pumps, complete with rails, lines and injectors. More valuable is that I have a brief history on how they failed.
I will update with findings of contamination in the rails and injectors. dweisel has inspected rails and injectors in previous posts, and indicated contamination.
.
specsalot and others have been curious about what has been captured in the Return Line Filter setup on my car.
After draining the return filter into a cup, small metallic particles are always visible. These have been trapped and not allowed to return to the tank or clean side of the filter when cold.
I have been experimenting with the Temperature circuit bypass with success and will post details after more tests.
I have also filtered the 62psi Auxiliary pump output, before it enters the HPFP -But that is another post!!
All the Best,

Good NewsW! So much for Bosch's self alignment design. Fail of epic proportion.

scdevon · Apr 19, 2012

Niner said:
Good NewsW! So much for Bosch's self alignment design. Fail of epic proportion.

I am not a Bosch apologist, but self alignment works as long as the piston doesn't seize. Piston seizure starts the ball rolling to pump failure. This pump suffered piston seizure first, then cam and roller failure. The pump in the pictures was horribly abused by having some low lubricity liquid pass through it. (Gasoline or water) Look at the wear on the shaft area of the cam and the cam support bushings.

Niner · Apr 19, 2012

Oops 2010 touareg V6 TDI, 37k miles, California fuel. Today at a so cal dealership in Los Angeles.

GraniteRooster · Apr 19, 2012

Niner said:
Oops 2010 touareg V6 TDI, 37k miles, California fuel. Today at a so cal dealership in Los Angeles.

Yeeeeoow..... a little swarf contamination, eh?

sgoldste01 · Apr 19, 2012

Misfueled? Low quality diesel?

El Dobro · Apr 19, 2012

Crappy HPFP?

specsalot · Apr 19, 2012

Got to love those POS tamper proof black plastic caps on the HP pump sections. 37k miles and barely 2 years old is a pretty disappointing lifespan. Every failure improves the odds that VW and Bosch will be forced to address this issue.

kjclow · Apr 20, 2012

And I keep hoping that every mile I put on mine puts me closer to not having a failure. I know, I'm living in a dream world.

Jack Frost · Apr 20, 2012

Every part on any car has a "best before" date written on it somewhere. You just can't see it. So it is always a question which part gives up first! Any HPFP will fail eventually, but will it be something else that causes you to sell the car to have it cut up for scrap?

Now in building of chaises, I tell you what,
There is always somewhere a weakest spot, —
In hub, tire, felloe, in spring or thill,
In panel, or crossbar, or floor, or sill,
In screw, bolt, thoroughbrace, — lurking still,
Find it somewhere you must and will, —
Above or below, or within or without, —
And that's the reason, beyond a doubt,
A chaise breaks down, but doesn't wear out.

- The Deacon's Masterpiece by Oliver Wendall Jones (1858)

scdevon · Apr 20, 2012

El Dobro said:
Crappy HPFP?

Sometimes, but mostly it's a soccer mom (or dad

) misfuel.

Look at the number of people on this site who subconsciously talk about their TDI's "gas" mileage" and how their TDI is "acting like it's not getting gas" when they step on the accelerator and the accuracy of their TDI's "gas gauge" and so on........

Almost nobody is going to admit that they misfueled a TDI while looking down the barrel of a $8k to $12k repair bill.

oilhammer · Apr 20, 2012

In some English-speaking nations, the word "gas" simply means fuel, it could mean petrol or diesel. Not all countries use the term "gasoline", therefore do not attribute "gas" as a shortened term. I very much doubt every TDI owner that uses the word is chronically misfueling their car.

eddif · Apr 20, 2012

oilhammer said:
In some English-speaking nations, the word "gas" simply means fuel, it could mean petrol or diesel. Not all countries use the term "gasoline", therefore do not attribute "gas" as a shortened term. I very much doubt every TDI owner that uses the word is chronically misfueling their car.

LOL ......I agree.

However

Due to the non-robust HPFP on VW CR TDIs, I do suggest every trick in the book be used to remember you are supposed to be putting Diesel into the tank.

If someone strange is to fuel your vehicle, I suggest repeating every phrase / word / memory clue you can think of, to make sure the correct product enters the tank. Ribbons, stamps on hands, paint, etc. Be nice doing the filling, but the end result of the wrong fuel will tend to make you wish you had tied some strange color ribbon to jog everyones memory. This might even be us if we are running a 103 degree fever and have had the worlds worst day just about fuel up time (lol the strange person might be us) .

eddif

sgoldste01 · Apr 20, 2012

I've got one of these hanging from my fuel cap. Can't miss it.

http://forums.tdiclub.com/showthread.php?t=319645

flyboy320 · Apr 20, 2012

sgoldste01 said:
i've got one of these hanging from my fuel cap. Can't miss it.

+1....

Niner · Apr 20, 2012

Highly unlikely at 2 years old and 38k miles that this was a misfuel, too much history of positive, correct, sucessful fueling. Fuel gauge showed not quite 1/2 a tank left. Plus, this belongs to an educated Penn State Grad... that has to be worth something, right?

Niner · Apr 20, 2012

scdevon said:
Sometimes, but mostly it's a soccer mom (or dad) misfuel.
Look at the number of people on this site who subconsciously talk about their TDI's "gas" mileage" and how their TDI is "acting like it's not getting gas" when they step on the accelerator and the accuracy of their TDI's "gas gauge" and so on........
Almost nobody is going to admit that they misfueled a TDI while looking down the barrel of a $8k to $12k repair bill.

Think this is around 15k, it's a Touareg, ya know. VW likes the repair bill to 5 year KBB value to be around 50%, so your car gets a trip to the scrap yard once out of warranty and you have to buy a new one from them again. It's a business model for them.

CR engine HPFP analysis

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