piper109
Veteran Member
- Joined
- Dec 6, 2003
- Location
- Ashe Co NC
Pics of your in tank unit would be really useful thanks!
Last edited:
There have been water separators in filters of past tdi models but the Common Rail models do not have them. This has fueled concern (yes pun intended) that there is inadequate protection for the delicate HPFP systems in these late models, one of which I see you have.Isn't the water separator incorporated into the fuel filter housing?
http://www.tdiclub.com/TDIFAQ/TDiFAQ-7.html#b
http://www.myturbodiesel.com/1000q/a5/2009-2010-VW-TDI-
fuel-filter.htm
piper109,From Piper109:
Pics of your in tank unit would be really useful thanks!
That is not entirely accurate. There was NOTHING special about the fuel filter/water separators on earlier generation TDIs. Water simply collects at the bottom of the filter and can be drained through the petcock. Many people have incorrectly assumed over the years that because several ounces of liquid came out, that they drained several ounces of water. In some extreme cases this may have been true, but opening that petcock allows the entire contents of the filter to drain--water and fuel. I put ~200k on my two ALHs and never found more than a droplet of water when draining/changing their fuel filters. I had similar results with my '80 300SD, Audi 5000 Diesel, and several Diesel Rabbits.There have been water separators in filters of past tdi models but the Common Rail models do not have them. This has fueled concern (yes pun intended) that there is inadequate protection for the delicate HPFP systems in these late models, one of which I see you have.
There is anxiety over the quality of the US diesel fuel supply and its worth the effort to be discriminating in this regard.
Steve
Steve - If you look at 2micron's pictures there appears to be a "spare" (unused) spud on top of the fuel sending unit cover. therefore you only need to add one additional penetration to the cover itself. I'm assuming you will want your kidney pump to circulate all fuel in the tank not just recirculate the changing contents of the sending unit? Dweisel has pointed out that you shouldn't open up the sending unit unless you've pulled your tank down (at least below 1/2) or you can wind up with a real mess.Well I'm thinking of doing things a little differently.
My plan is to use a kidney circuit by adding two pipes going through the lid of the tank unit, one going close to the bottom of the tank and the other close to the top.
Steve
That's exactly what it is. The Mk2 Diesels had a water trap under the body of the car, but it proved unreliable and problematic. Fuel swirling in the filter will always precipitate out water and other contaminants. That's why they filter from outside to in.It begs the question: what is a water separater?
The fuel tank is a water seperater. So is the fuel filter housing. My tracter has a petcock at the bottom of the fuel tank and I drain a bit of liquid there once in a while, but I never know if it had any water in it. The fuel filter is made out of clear plastic but I never see any water in it, but given I drain the fuel tank periodically, there should not any.
I believe the water seperater for our TDIs is the fuel filter. It is doubtful, given the surface tension of water, that any water would get through the fuel filter medai. If we just worry about changing the fuel filter and remove any water that may have collected in the bottom of the housing, I think we should be fine.
I would suspect that industrial Diesels have dual filters and sensors because the fuel source is probably not as reliable. Most commercial fuel stations have underground fuel tanks, so the temperature of the tank/fuel should stay pretty constant. Assuming there are no cracks or other ways for water to seep into the tank, there should be very little water accumulation.All industrial diesels that I have seen usually have two filters and recently have sensors which indicate on the ECM's that water is present in their primary filters and throw a check engine code or warning. It is surprising to me that VW does not do something similar given the heightened sensitivity of the equipment.
That's the $64,000 question though. The Fuel Pressure Regulator controls the pressure in the rail, so how will more/less fuel flow affect it? Will increased demand on the Aux Pump be a problem?These are good points and I had already come to the idea of using that spud myself. Yes there is some kind of eductor in there (per Dang144) so I would plan to go around the whole unit with the pick-up tube and allow the fuel to flow in the top, perhaps even teeing into the return line. The 1/2 gal/min max extra flow would probably not affect much. Ideally I would like the lift pump to pick up freshly filtered fuel.....probably a long shot.
I am still selecting a fuel filter with suitable WIF sensor circuitry. Once that is lined up I will dig into the tank myself.
Steve
Surface tension is the attraction that water molecules have for each other in the liquid form. Because of the structure of the water molecule, it has one of the highest surface tenision properties of almost any liquid. The only liquid that I know that has more surface tension than water is mercury.... I can't speak to the physics of a fuel filter re: surface tension and water passing through the media.
Your comment dos not specify the form of the water content of the fuel that is being pumped. It could be dissolved, emulsified, or just two mixed liquids. However, if it is safe to say that most liquid water in fuel would certainly be emulsified to various degrees after going through a pump. Some of that emuslifed fuel would dissolve into the fuel.they state that the action of pumping the fuel with a water content creates an emulsion of fuel and water which renders the water separators ineffective and the water remains in the fuel.
Pumps that I know "push liquids" through a filter. If they try to suck it through the filter, the pumps cavitate (emulsifying air into the liquid) and are limited to applying a pressure of only a few psi across the filter before a vacum is created inside the filter. If pumps cavitate and emuslify air, then the fuel/water seperater now becomes a fuel/air seperater. Entrained air is even worse for the injecters than water.They say then that it is necessary to draw fuel through the filter by installing the filters/separators on the suction side of pumps, preventing the formation of an emulsion and enabling the water separators to do their work by the principles you have outlined. Presumably the pumps are doing the very thing that you explain is difficult to do.
There must be a filter though before the fuel enters the injecters. Many of these older diesels were fueled from tanks under the owner's control and maintenence. Not so for our cars.Many older diesels do in fact have lift pumps in the injector pumps that draw fuel all the way from the tank instead of having pumps in the tank that feed the injection system.
Well, it has been just under 8k using the filter and all is well.Hello MayorDJQ,
Yes you are correct, this smaller filter is after the pressure relief valve. It only captures contaminants after the rail and prevents them from circulating to the tank. The line pressure is 9 psi, 159 litres per hour. (42 us gal/ hour)
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Thanks again for the comments, and sure,
red64chevelle, experiment with a lighter setup, just ensure your filters meet the flow rates posted earlier.
Thanks!!!
Contact 2micron to see if he is selling kits. I got one from him months ago. I have been very happy with it. As he has stated, it does not remove any water, as the factory filter gets all of that.Is there a kit for the return filter setup or is it a pieced together kit?
Haven't read to the end, of this thread, but this quote caught my eye.I forgot another one:
* Improper run-in at the factory.
I would guess that Bosch does a bench test of these little piston-engines at their assembly lines, before being shipped to VW. A full operational test before it leaves their facility. It may be that certain batches have had problems. Maybe due to improper machine settings, or assembly personnel error.
I think it's much more likely to be something like this than some sort of wear due to the fuel lubricity and/or minute particles in the fuel. Why have some HPFP's failed at only 7k miles? They have had such a small amount of fuel run through them -- that's only 10 or so tanks. You're telling me that 10 tanks of quality fuel, filtered to the VW filter specs, was enough to kill an HPFP? And there are many, many CR TDI's with 50k, 80k, 100k+ miles on them that are running just fine, having filtered much more fuel, and likely even seen a few tanks of lesser quality fuel?
No, I'd be much more willing to bet that there was a pump tolerance issue, or mis-hardened pistons, or some occasional issue with pump assembly or run-in that's the cause of the HPFP failures.
As I said, you're free to filter out the minutia if you like. But as for me, I think I'll put my faith in the VW/Bosch engineers to root-cause the issue, rather than slap on band-aids that no one has any good reason to believe will be beneficial.
Let's see, this thread was in progress back in 2012. Failure rates were low back at the launch of the vehicle, and they are even lower now. I'd say that things are improving.Haven't read to the end, of this thread, but this quote caught my eye.
It has been a couple of years and well I think they aren't trying as hard as they should on getting to the root cause. With their technology and expertise I figure a couple of months to address an issue this small, if anything it seems to have gotten worse.
You have had some good things to say as well as a number of other people but I think your faith might be a little miss placed.
I'm thinkin 2micron might be onto something a little more concrete in the way of preventative maintenance till the engineers finally get around to getting to the root cause.
Another thing he is doing is engineering a replacement for the root cause. Replacing the cp4 with a cp3, an he seems to be doing on a much smaller budget.
(My statements are my opinions based on my experiences)