If I were one of the unlucky 1% with a HPFP failure? Trade it in at the nearest unsuspecting dealer after confirming that there was glitter in the fuel system as long as it was still running ok. LMFAO
(Spare me the ethical lectures).
CR engine HPFP analysis
- Thread starter oilhammer
- Start date
(Spare me the ethical lectures).
sgoldste01
Veteran Member
- Joined
- Mar 14, 2010
- Location
- Webster, NY
- TDI
- None; Replaced 2010 Golf TDI with 2012 Subaru Impreza 5-door with manual tranny
What's wrong with you? What part of being a good person don't you understand?
Just kidding. I'd be tempted to do the same thing.
eddif comments in blue
bluey;3784795]A small ceramic or perhaps preferentially sintered stainless steel filter to directly replace the cylindrical fuel metering valve protection screen is not normally doing any filtration duties. Under normal operation, only clean fuel passes through that. So I can't see why a small filter that prevents downstream injector damage needs to be any bigger than the screen. If it clogs, then the engine will shut down, which is not a bad option.
I can be wrong but:
every bit of fuel the car burns over time goes through that little screen. Since the total burned fuel and rail overflow goes through the small screen, there is trash going through the screen stock. When you put in the better ceramic better filter all the small trash that has been going through the screen will be building up on the outside of the ceramic or other filtering medium). IMHO, over time, there will be more collection of materials and the shut down will occur pretty quick if wear starts. Also while this is going on the tank is getting tiny and larger wear materials.
++++++++++++
The bypass valve is the only potential flush mechanism, but can't be used for flushing without passing the swarf through the valve, which doesn't really work without risking valve malfunction.
Stock they leave the screen course and in fact are risking the whole system. Also even course the stock screen can clog on larger particles.
+++++++++++++
To be able to effectively filter swarf through creating a "cleaning" circulation requires the bypass valve function to be taken off-board so the pea-sized screen can be replaced by a somewhat larger filter and still permit the bypass valve to operate.
Which is exactly what all the previously described added adapters and added filter do:
1..the added filter filters the wear material before it hits the pressure valve, and filters the fuel going to the quantity fuel regulator valve.
2..Once the trash is removed it will not stop up the re-located valve (it can still have the pea size filter.
+++++++++++++
So to me, if one wishes to use an adapter to permit filtration of swarf from being stirred round the HPFP body, it should go where the overflow valve goes in preference to where the fuel metering valve goes which cannot provide any bypass circulation.
You are doing it with two filters where one added filter can filter the fuel for two places. Both methods do not stop a HPFP failure and only protect the other areas of the car. The adapter method should allow the quantity fuel supply valve to have clean fuel supplied to it. In fact with an added filter supplying your ceramic filter with clean fuel, the ceramic filter should live through a HPFP failure. Keeping track of the HPFP noise would then be the alert for pump failure, rather than a fuel shut down.
+++++++++++++++
eddif comments:
There are several ways to do all the filtering. The adapters and one added filter is just my choice. It allows you to:
1..watch the pressure differential on the HPFP bushings.
If you have another plan I would be interested to see how you would handle the pressure differential. Please post your fuel flow diagram and explanation.
2..filter the return fuel before the thermostatic stock fuel filter
3..filter fuel going to the HP piston (by filtering the fuel before the quantity fuel control valve)
4..We can at this point modify things to work more like the 2012 Passat system (no real problem, And you could take care of several issues).
eddif
bluey;3784795]A small ceramic or perhaps preferentially sintered stainless steel filter to directly replace the cylindrical fuel metering valve protection screen is not normally doing any filtration duties. Under normal operation, only clean fuel passes through that. So I can't see why a small filter that prevents downstream injector damage needs to be any bigger than the screen. If it clogs, then the engine will shut down, which is not a bad option.
I can be wrong but:
every bit of fuel the car burns over time goes through that little screen. Since the total burned fuel and rail overflow goes through the small screen, there is trash going through the screen stock. When you put in the better ceramic better filter all the small trash that has been going through the screen will be building up on the outside of the ceramic or other filtering medium). IMHO, over time, there will be more collection of materials and the shut down will occur pretty quick if wear starts. Also while this is going on the tank is getting tiny and larger wear materials.
++++++++++++
The bypass valve is the only potential flush mechanism, but can't be used for flushing without passing the swarf through the valve, which doesn't really work without risking valve malfunction.
Stock they leave the screen course and in fact are risking the whole system. Also even course the stock screen can clog on larger particles.
+++++++++++++
To be able to effectively filter swarf through creating a "cleaning" circulation requires the bypass valve function to be taken off-board so the pea-sized screen can be replaced by a somewhat larger filter and still permit the bypass valve to operate.
Which is exactly what all the previously described added adapters and added filter do:
1..the added filter filters the wear material before it hits the pressure valve, and filters the fuel going to the quantity fuel regulator valve.
2..Once the trash is removed it will not stop up the re-located valve (it can still have the pea size filter.
+++++++++++++
So to me, if one wishes to use an adapter to permit filtration of swarf from being stirred round the HPFP body, it should go where the overflow valve goes in preference to where the fuel metering valve goes which cannot provide any bypass circulation.
You are doing it with two filters where one added filter can filter the fuel for two places. Both methods do not stop a HPFP failure and only protect the other areas of the car. The adapter method should allow the quantity fuel supply valve to have clean fuel supplied to it. In fact with an added filter supplying your ceramic filter with clean fuel, the ceramic filter should live through a HPFP failure. Keeping track of the HPFP noise would then be the alert for pump failure, rather than a fuel shut down.
+++++++++++++++
eddif comments:
There are several ways to do all the filtering. The adapters and one added filter is just my choice. It allows you to:
1..watch the pressure differential on the HPFP bushings.
If you have another plan I would be interested to see how you would handle the pressure differential. Please post your fuel flow diagram and explanation.
2..filter the return fuel before the thermostatic stock fuel filter
3..filter fuel going to the HP piston (by filtering the fuel before the quantity fuel control valve)
4..We can at this point modify things to work more like the 2012 Passat system (no real problem, And you could take care of several issues).
eddif
RNDDUDE
Veteran Member
eddif, good comments. There have been a lot of comments saying that filtering the HPFP debris would not prevent a failure, but I am of the opinion that it might greatly reduce the failure timeline even after the pump has started to show wear. My rational is that the current system allows a 'cascading event' where the swarf created stays in the pump and creates more swarf due to it's abrasiveness. If the swarf is filtered out, the pump failure might become much more progressive and slower. Whether it could be slowed significantly, and whether that would even make a difference in stranding you along side the road is debatable.
Spliting flows (circulation v.s. combustion fuel) through the pump with adapters would primarily be done to add filtration that protects the balance of the fuel system outside of the HPFP Low Pressure Body.
A. Sintered SS element protecting the HP end (added protection).
B. Filtration of Combustion Fuel prior to the FMV (fuel metering valve).
C. Filtration of pump return fuel prior to the OEM fuel filter.
These are all good things that help limit damage by swarf outside of the HPFP Low Pressure Body section. This does little or nothing to address what happens inside the LP Body itself. Instinctively we all understand that this is where the "cascading failure" is taking place. Everything else is collateral to the damage that occurs in this section. I'm not against these measures, but recognize they are not fixes.
Next step (already discussed in this thread) would be the elimination of diesel fuel in the LP body. This can be done with almost the same type of adapters. This would likely need to be a stand alone system because engine oil may not work well due to oil contaminants present. Three issues arise:
1. Providing an oil that can lubricate in the very close clearances present. Oil specification needs very careful attention as clearances are less than 0.001" on most parts.
2. Developing the balance of the lube oil circulation system (pump, sump, heat exchanger) for the HPFP.
3. Fuel dilution of HPFP lube system due to HP piston leak down. How to handle this.
Will the pump still be subject to the same failure issues if lubricated by a light oil? The ultimate question. I suspect the longevity would be significantly improved.
A. Sintered SS element protecting the HP end (added protection).
B. Filtration of Combustion Fuel prior to the FMV (fuel metering valve).
C. Filtration of pump return fuel prior to the OEM fuel filter.
These are all good things that help limit damage by swarf outside of the HPFP Low Pressure Body section. This does little or nothing to address what happens inside the LP Body itself. Instinctively we all understand that this is where the "cascading failure" is taking place. Everything else is collateral to the damage that occurs in this section. I'm not against these measures, but recognize they are not fixes.
Next step (already discussed in this thread) would be the elimination of diesel fuel in the LP body. This can be done with almost the same type of adapters. This would likely need to be a stand alone system because engine oil may not work well due to oil contaminants present. Three issues arise:
1. Providing an oil that can lubricate in the very close clearances present. Oil specification needs very careful attention as clearances are less than 0.001" on most parts.
2. Developing the balance of the lube oil circulation system (pump, sump, heat exchanger) for the HPFP.
3. Fuel dilution of HPFP lube system due to HP piston leak down. How to handle this.
Will the pump still be subject to the same failure issues if lubricated by a light oil? The ultimate question. I suspect the longevity would be significantly improved.
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You are right I did try and push for a seperate system here and at least one other site. No one seemed interested. A 0 weight oil might be fine.
This was my response to Ski on 11-20-10
I think since the 2012 Passat seems to be doing ok we should consider:
1..Putting the booster before a filter helps. We have discussed the screen between the previous booster pump and the HPFP---along with discussing the booster pump possibly shedding metal. The screen could not be getting all the trash from the booster pump. We might ought to consider a tank pump or add a filter between the booster pump and the HPFP. This filter could help the life of the HPFP. I watched, IMHO, trash from the rollers on the PDs go between the valve followers and lobes as star trails (got no comments from others). Any trash going to the CR HPFP Could be a source of scratches on the rollers. The gasoline may effect the booster pump more than we know.
2..If we go to a tank ~65 psi pump we may not need the thermal valve on the fuel filter.
3..IMHO, the first generation filter should not be on any car owned by a club member. There is too much chance of the seal being folded / crimpted / wrinkled during a filter change. I like the water drain, but few probably use it anyway. A new deeper canister with drain, and the second generation filter should be better. Looking at the thickness of the filter cases, I wonder if VW considered ~65 psi going through the filter at one time. #1 added filter above would protect the HPFP from stock filter seal leakage.
The Passat shows that ~65 psi works in fuel filters (that was always a major question for me. Adding filters in ~70 psi should not worry us anymore.
Time is slipping away. Warranty end is here for more and more.
eddif
1..Putting the booster before a filter helps. We have discussed the screen between the previous booster pump and the HPFP---along with discussing the booster pump possibly shedding metal. The screen could not be getting all the trash from the booster pump. We might ought to consider a tank pump or add a filter between the booster pump and the HPFP. This filter could help the life of the HPFP. I watched, IMHO, trash from the rollers on the PDs go between the valve followers and lobes as star trails (got no comments from others). Any trash going to the CR HPFP Could be a source of scratches on the rollers. The gasoline may effect the booster pump more than we know.
2..If we go to a tank ~65 psi pump we may not need the thermal valve on the fuel filter.
3..IMHO, the first generation filter should not be on any car owned by a club member. There is too much chance of the seal being folded / crimpted / wrinkled during a filter change. I like the water drain, but few probably use it anyway. A new deeper canister with drain, and the second generation filter should be better. Looking at the thickness of the filter cases, I wonder if VW considered ~65 psi going through the filter at one time. #1 added filter above would protect the HPFP from stock filter seal leakage.
The Passat shows that ~65 psi works in fuel filters (that was always a major question for me. Adding filters in ~70 psi should not worry us anymore.
Time is slipping away. Warranty end is here for more and more.
eddif
You're right, of course, but this is impractical to do with the current design. There is no way to isolate the crankcase of the pump that you would be running lube oil in from the high pressure piston (rod) that supplies the fuel rail. The engine would slowly consume the lube oil from the pump crankcase. Even piston rings on the cam follower piston wouldn't be a positive enough of a seal to prevent the engine from consuming the lube oil.
I always assumed the bigger issue would be oil dilution by fuel leaking down in the clearances of the HP section. This option is not ass far fetched as you might imagine. The biggest challenge would be to have a system that could manage seasonal temperature variations.
That is actually helpful. Once out of warranty there will be more folks willing to modify their fuel systems.
Ski in NC
Top Post Dawg
Many engines have injection cams, etc lubed with engine oil with no problem keeping fuel and lube separate. The machined clearance on the plunger rod is so tight that there is no significant migration. No seals there. Lube oil on one side of plunger, fuel on the other.
Examples of engines set up this way: Kubota, yanmar, some cummins, MAN, volvo, vw pd, etc, etc.
The above are jerk pump engines. No reason same could not be done with common rail.
Only issues I've seen for fuel dilution were worn out enblock unit pumps on CAT auxiliary engines. Oil manufacturer provided flow sticks to test [viscosity race] old engine oil against new. Oil change was based on negative test results rather than engine hours due to low duty cycle of these engines. I agree that this is probably not a big concern for CR system modification.
I know what a jerk pump is. A CR is not plumbed that way. A CR is impractical to convert to a jerk pump configuration.
Ski in NC
Top Post Dawg
I guess I was not too clear. I didn't mean convert cr to jerk pump, I meant convert cr pump from fuel lube to oil lube.
Are you talking about having a closed sump in HPFP filled with lube oil or having the HPFP share circulated, filtered engine oil with the engine?
Both ideas are impractical with the current CR architecture. A closed sump would get quickly diluted from even microscopic amounts of fuel migrating from the high pressure portion of the pump. A HPFP sump could only hold a few ounces of lube oil at best. This small quantity of oil would quickly sheer down from heat and pressure and become a worse lube than diesel fuel.
Shared engine oil? How would you accomplish this with the current CR fuel circuit? Piezo injectors won't tolerate even microscopic contaminants from engine oil. Engine oil is filthy dirty by CR fuel system standards. Engines that run "Jerk Pumps" don't have Piezo injectors running at 1800 bar (26,000 psi) fuel pressure.
The only way to really do this right would be to have a separate oil circulation system for the HPFP. Separate oil tank, heat exchanger, oil circulation pump and oil filter. If dilution is a factor, then you just need to change oil periodically in the system.
The following changes would be required:
1. FMV (fuel metering valve) would have to bolt to an adapter inset in the pump body. This would segreate the combustion fuel from the rest of the pump.
2. Lubrication oil would be supplied at the current fuel inlet hose barb to the HPFP.
3. Lubrication oil outflow would be taken out of the LP Body in two locations: Main flow though an adapter inserted into the port which held the Fuel Overflow Valve. Secondary (pump bearing) flow through the current fuel recirculation port. This needs some careful review in order to insure that you can obtain good bearing oil flows for the final system.
4. The existing Fuel Overflow would continue to peform it's current function of controlling fuel pressure supplied to the FMV. It will have to be located into a stand alone adapter. The adapter would be fed through the current protective fuel screen / temperatuer sensor unit. Recirculation fuel would exit the downstream side of the adapter after it passed through the Overflow Valve.
By setting up this kind of arrangement, it makes it possible to easily add supplemental fuel filtration to the combustion and recirculation paths. If you dig back in this thread there are some sketches / diagrams of revised flow paths. The biggest challenge would be to have a system that performs as intended in both winter and summer. An oil lubed pump will likely experience greater heat generation because of oil viscosity. The sizing of the oil cooler would be an interesting problem.
Unfortunately this represents a lot of development effort for solutions that basically cannot be sold to anyone who wants to maintain warranty coverage. Most of the installed base of these HPFPS are still under warranty coverage. The other bottom line is that if issues with this pump are primarily metalurgical / design rather than being fuel related, oil lubrication is still not really addressing root cause. Bosch and VW know the truth but aren't talking (too much product liablity involved).
Going commercial means essentially owning product liability for this kind of retrofit solution. At the end of the day, being retrofitted to pumps with hours / miles means there will still be failures. Who ever goes down this route better not scrimp on the budget for drafting legal disclaimers.
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I think the only reasonable solution is to work with the current design with durable anti-friction coatings on the internals.
We have a theory about these pumps anyway. The cam roller isn't what fails at first. The cam roller fails when it loses orientation or gets fouled with aluminum glitter from the pump bore. The root cause of this is sticking of the cam follower piston in the bore. Someday soon we will know that there was poor quality control with these pump housings in the beginning. If the bore clearance was correct in the beginning with early pumps, that quickly changed due to poor pump metallurgy causing the bore dimension to change (possibly tighten up) due to the dimensions of the housing changing into an egg shaped bore (?) There was also poor quality control with regard to anti-friction coatings (if any were used).
Low lubricity fuel doesn't help with any of this, but I think some pumps would have failed with the lubricity of straight Bio B100. These early pump bores were waaaay out of spec, I suspect. By the time a pump is smoked, there's no real way of telling what the piston to bore clearance was prior to failing anyway.
I GUARANTEE you that Bosch got things right with these latest "Czech Republic" Bosch pumps on 2012+ cars. None of these pumps have failed that I know of. I'd love to tear into one of these new Czech made pumps without spending the money to do it.
We have a theory about these pumps anyway. The cam roller isn't what fails at first. The cam roller fails when it loses orientation or gets fouled with aluminum glitter from the pump bore. The root cause of this is sticking of the cam follower piston in the bore. Someday soon we will know that there was poor quality control with these pump housings in the beginning. If the bore clearance was correct in the beginning with early pumps, that quickly changed due to poor pump metallurgy causing the bore dimension to change (possibly tighten up) due to the dimensions of the housing changing into an egg shaped bore (?) There was also poor quality control with regard to anti-friction coatings (if any were used).
Low lubricity fuel doesn't help with any of this, but I think some pumps would have failed with the lubricity of straight Bio B100. These early pump bores were waaaay out of spec, I suspect. By the time a pump is smoked, there's no real way of telling what the piston to bore clearance was prior to failing anyway.
I GUARANTEE you that Bosch got things right with these latest "Czech Republic" Bosch pumps on 2012+ cars. None of these pumps have failed that I know of. I'd love to tear into one of these new Czech made pumps without spending the money to do it.
Ski in NC
Top Post Dawg
Agreed, this is not a simple re-arrangement of plumbing. To use lube oil, it has to be designed that way from the start. Or if a mod, it would be a quite significant.
But disagree that this is not plausible because of possible contamination of injectors. Oil simply does not migrate through plunger/barrel fit.
With system designed as is, there is swarf ALREADY going into injectors!!
flyboy320
Veteran Member
Unfortunately there has been at least one as posted in the HPFP failure thread.
GoFaster
Moderator at Large
Oil might be resistant to such migration, but fuel won't be. Trace amounts of fuel will leak through the clearance between plunger and bore, however small that clearance may be.
I am not sure, but I suspect the old "jerk pumps" that had separate lubrication for the bottom end of the pump used a mechanical seal between the fuel zone and the lube zone, which the plunger has to pass through.
It's worth noting that the VW P-D injectors have the plunger pass through the fuel return passage (next to no pressure in it) before they pass into the main pressure chamber. Any fuel that leaks past the plunger due to the very high pressure in the pumping chamber leaks harmlessly back to the fuel return passage. This way there is next to no pressure differential across the part of the plunger that separates two different fluids (engine oil on the outside and fuel on the inside).
http://www.zamslube.com/pd_diagram.jpg - note that the groove around the plunger up at the top is connected to a passage that goes back to the fuel return passage between the two O-rings on the outside.
Yes, I know a common-rail pump isn't a P-D pump. But it's a piston pump (and one that operates in the same pressure range) and the same concept could be applied ... but it would require an entirely different layout for the pump.
sgoldste01
Veteran Member
- Joined
- Mar 14, 2010
- Location
- Webster, NY
- TDI
- None; Replaced 2010 Golf TDI with 2012 Subaru Impreza 5-door with manual tranny
Are dealers replacing failed HPFPs with Czech pumps these days?
flyboy320
Veteran Member
To save me from going back and reading tones of pages, can someone tell me or post pictures to how to look/access the HPFP to see where it's made?
Softrockrenegade
Veteran Member
- Joined
- Aug 25, 2011
- Location
- Howellbama, NJ
- TDI
- None...2011 Golf DSG (replaced by VW W/) 2013 Passat SE 6M(bought back) Current 2017 sportwagen TSI 4Motion.
Gotta snap a pic of the underside of the pump . Kind tricky but isn't a problem with a slim camera or iPhone
Plus 3 Golfer
Veteran Member
Yep^.
Look at the first few posts here. You can hold a small camera just under the front of the HPFP and snap a few pics.
http://forums.tdiclub.com/showthread.php?t=292910&highlight=HPFP+tag
Look at the first few posts here. You can hold a small camera just under the front of the HPFP and snap a few pics.
http://forums.tdiclub.com/showthread.php?t=292910&highlight=HPFP+tag
Ski in NC
Top Post Dawg
The jerk pump systems have something similar to the pd- the helix spill port keeps injection pressure off the lower part of the plunger. The same thing should be done with an oil lubed CR pump. Some sort of vented annular groove below pumping element, tied to lp fuel supply. Not a difficult feature... at least in the design stage!!
None of the oil lubed jerk pumps I have been into (lots) have any other type of seal on the plunger.
There may be some migration, but remember that these engines often accumulate a couple % fuel dilution just from fuel condensing on combustion cylinder walls. So a minute amount from the fuel pump should be no big deal.
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flyboy320
Veteran Member
Thanks Softrockrenegade and Plus 3 Golfer, I'm gonna look in the next few days. Mine was built in Jan. 2012, so we'll see....
Also interesting to see the last few failures have been in the warmer climates, that seems to be a trend from the last few years.
Also interesting to see the last few failures have been in the warmer climates, that seems to be a trend from the last few years.
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If you do a full blown stand alone oil lubrication system, this issue goes to zero - You just have to change the oil periodically.
Great observation - Excellent Linked Picture - This has caused me to rethink the leak down as a potential issue. Thanks for posting it.
dweisel
Top Post Dawg
Is it just me. Or does the hpfp failure season seem to kick off in TX every year.Are fuel temps a contributing factor to failures?