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Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKVI-A6 Golf family including Jetta SportWagen (~ 2010+)

VW MKVI-A6 Golf family including Jetta SportWagen (~ 2010+) Discussions area for A6/MkVI (2010+) Golf and Golf Wagons (Jetta Sportwagon in the USA).

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Old June 10th, 2010, 06:05   #46
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Quote:
Originally Posted by oilhammer
Someone in another thread eluded to the fact that the roller piston could rotate and be riding at right angles to the shaft, and sure enough, I confirmed here that yes it can, there is NOTHING I can see to keep the piston aligned properly with the shaft cams.

And that would explain the strange wear marks I have on this little roller.

Updated original post with more pics.
Thought some more about this:

Based on the picture of the cam lobe, I don't think this is happening. The wear on the cam lobe is very uniform and it appears to be exactly the width of the roller on the piston. If the piston/roller is rotating and hitting the cam at an angle, wouldn't that produce a cam lobe that has more wear in the center, in more of a cup form, than straight even wear across the top?
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Old June 10th, 2010, 06:21   #47
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Quote:
Originally Posted by cevans
Thought some more about this:

Based on the picture of the cam lobe, I don't think this is happening. The wear on the cam lobe is very uniform and it appears to be exactly the width of the roller on the piston. If the piston/roller is rotating and hitting the cam at an angle, wouldn't that produce a cam lobe that has more wear in the center, in more of a cup form, than straight even wear across the top?
Yes, you are correct, but if the piston went sideways right before catastrophe, it may not show much wear on the shaft's cam lobes. Remember, these cars go from running fine to not running almost within a mile or so, as least as I understand it.
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Old June 10th, 2010, 06:35   #48
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Quote:
Originally Posted by saucer
Sorry I got carried away with the FSI info - I thought some might find it interesting
I found it interesting. It seems that the only thing the DLC coating is good at in these pumps is wearing away

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As I mentioned though, the FSI HPFP is very easy to access and inspect. Is that not the case here?
I don't think so. The cam/piston is internal to the pump. Generally, the internal components of a diesel injector pump are thought to be of such tight tolerances that they are cannot realistically be inspected or repaired by mere mortals. I'm assuming this is the case here, although from the pics it looks so darn crude and simple in there.

There are shops that specialize in rebuilding pumps (such as DFIS). It would be fascinating to have one of these failed pumps sent to be rebuilt, and hear what they would have to say as well.

Say, I wonder if there are any bosch-certified service centers that have experience with these things. It would be neat to hear what they have to say about them in general. (e.g. do they get a lot of them? Do they all look like this one, failing in generally the same way?)
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Last edited by birkie; June 10th, 2010 at 06:41.
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Old June 10th, 2010, 06:40   #49
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Is it possible that the damage to the roller is caused by 'hamering' of the HPFP plunger due too a bad functioning of (a) pressure control valve(s) or the injectors that are injecting quickly very small amounts during the powerstroke that causes 'hamering in the Common rail?
My 2c.
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Old June 10th, 2010, 06:47   #50
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Good point. Most CR systems (even on gassers) have some method of dampening these pulses.
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Old June 10th, 2010, 07:42   #51
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Quote:
Originally Posted by oilhammer
Yes, you are correct, but if the piston went sideways right before catastrophe, it may not show much wear on the shaft's cam lobes. Remember, these cars go from running fine to not running almost within a mile or so, as least as I understand it.
Yep, makes sense, would there be some indication of that - e.g. horizontal marks on the roller?

Is the pressure control valve visible in the photos?
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Old June 10th, 2010, 07:56   #52
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Quote:
Originally Posted by oilhammer
Good point. Most CR systems (even on gassers) have some method of dampening these pulses.
Some more information of damping in the common rail. It's for a gasser but you get the point.
http://delphi.com/manufacturers/auto...s/injsys/mpfi/
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Old June 10th, 2010, 12:21   #53
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I've read some questions on this thread that can be anwsered by the following pdf. Not sure how long this will remain on the web, so save a copy.

http://www.dsd.go.th/itrain/km/kboc/...il_BIN5_UL.pdf

See pages 26 - 41 for fuel system description and a nice overview of the HPFP operation. There are also descriptions of "Effect of Failures" for certain components.

Referring to page 33, I find it difficult to understand why the entire injector system needs to be rebuilt if the HPFP fails at the cam/roller interface. Notice that there are "fine filters" that will prevent metal from entering the high pressure rail. The only thing that should need to be changed is the HPFP ??? Something else in the HPFP needs to fail to require the injectors to be replaced (e.g. exhaust valve, top of pump piston, intake valve, etc).

Also, I think the pump piston is kept from rotating by the interaction of the roller with the cam. The force of the spring pushing on the roller should keep it in the right position as the cam rotates. There is probably a fine "wobble" that occurs, but this should be mitigated by the lubrication of the fuel. If the lubrication is not there and the roller starts to break apart, metal particles will clog the "fine filters" in the HPFP. First symptom would most likely be reduced power and then a complete shutdown due to lack of fuel.
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Old June 10th, 2010, 15:03   #54
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Very nice engine manual. Boy, things have gotten complicated in the last few years.
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Old June 10th, 2010, 15:17   #55
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Dang, Nimbus, great document! Thanks for the pointer!
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Old June 10th, 2010, 15:26   #56
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X2!!! Thanks. Saved it. And read it.
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Old June 10th, 2010, 15:27   #57
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Originally Posted by aja8888
Very nice engine manual. Boy, things have gotten complicated in the last few years.
Another thanks to Nimbus, what a great resource. Makes me want to hold on to my '75 240D. Simple can be good!!
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Old June 10th, 2010, 15:33   #58
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Quote:There is probably a fine "wobble" that occurs, but this should be mitigated by the lubrication of the fuel. If the lubrication is not there and the roller starts to break apart, metal particles will clog the "fine filters" in the HPFP. First symptom would most likely be reduced power and then a complete shutdown due to lack of fuel.

This makes sense to me and would explain why failure is sudden and catastrophic. The followup question would be how and why could a fuel starvation/lubrication condition occur at the cam roller interface?
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Old June 10th, 2010, 16:58   #59
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maybe the return check valves are opening too soon, and allowing the cam & roller in the pump to run dry.
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Old June 10th, 2010, 17:25   #60
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Another thanks to Nimbus, what a great resource. Makes me want to hold on to my '75 240D. Simple can be good!!
Yeah, and I am holding on to my Passat, too. I am a mechanical engineer and after spending a fair bit of time reading that manual, I can see why VW dealer repair shops can have their hands full with the complexity of the system. Plus, their dealing with gassrs 90+% of the time increases the unfamiliarity of the techs with it.
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