D3 A8 Fuel Filter Service Notes (2006 W12)
 

This one was pretty easy. Again, vehicle is approaching 95,000 miles and now 7+ years old so I want to roll through some of the rarely serviced items. I try to do fuel filters once or twice in the life of the vehicle. If it saves me a fuel pump(s) change, that's a bunch of diagnostics, hassle and $ for the posters who have been through it. I haven't lost a fuel pump since one very early CIS injected C1, and only one of my hand me down old Audis (a C3) needed a pump late on. W12's can flow a lot of fuel too, so all the more reason.

Fuel filter is tucked underneath below the right rear passenger (U.S. vehicle) door. At least on mine, there is an aero plastic panel that completely conceals it. As with my differential service, I still had the car on the ramps so proceeded to do this. A bunch of 10mm fasteners and a few snap clips hold it. All reusable if careful; just took a nut driver and small screwdriver to free the snap clips.

Once I got the panel off, the filter was right there. See second picture. Mine has the type with two openings on one side, and one on the outlet side. On the side with two, turns out the smaller diameter one near the edge is the apparent true inlet and is stamped "IN." I'm guessing the other one is some kind of smog/vapor port thing. Apparently in the relatively late W12's, the filter was changed to one with only one port on each side. Hard to track down the exact configurations here; either order by VIN or get under that cover to see what you really have. Other motors may well vary at part number level too.

FWIW, filter I pulled is the original almost certainly, with a manufacture date almost a year before the car was built. A "UFI" brand (never heard of that; made in Italy) with OE part numbers on it (obsolete, 4F0 201 511B). Replacement filter (see picture) was ordered by VIN as 4E0 201 511A, fit perfectly and looks virtually identical. I also first bought a Mann filter off of Amazon using a part # cross reference to WK720/3. Looks the same, same 3 ports, same one marked "IN." Same "4.0 Bar" pressure noted on it as on the one I pulled. But candidly, the "Made in China" marking didn't grab me, all the more since it's A6's from China, not A8's AFAIK, and the construction seemed a bit different at the ends than either the old or new Audi branded ones. So I ultimately passed on that Mann one. Usually I find Mann is identical and usually made in Germany, so this surprised me, especially for a pretty recent A8 with an unusual motor.

Lines came off pretty easily. First I opened the plastic filter retaining clamp up. Obvious in the picture below. A tri square type fastener, near 8mm in apparent size. No trouble with it stripping, not turning or anything as someone in a recent post noted. Actually it was almost loose to the touch when I first turned it. I squeezed the plastic pressure fit fuel line attachments lightly with a pair of pliers (at the points on the fittings sticking out a bit) as I tried to pull loose by hand. Pretty intuitive. I didn't want to break anything. They yielded fairly easily. As usual, I got the initial spray of pressurized gas as I cracked the first one. I try to always do these outside and well away from gas water heaters and such as a result. Also as usual, by the time I pulled all the lines, the filter was draining its gas no matter how fast I got the drain pan near.

Bolted filter back in. Then I started car before fitting cover to be sure no leaks at the connectors or otherwise. Fired up in 5 to 10 seconds and ran smoothly within first second or two. No leaks as expected, so I refit cover. Took a while to sort out the plastic washers associated with the 10mm plastic nuts, but it all made sense after a while (probably should have laid them out in order as I removed them, but I didn't realize there was an upper washer component that sometimes separated and sometimes didn't).

Observations/did I need to: as usual, I drained filter fully when done. Then I blew through it, from both inlet and outlet sides. Frankly, back pressure was pretty minimal; relatively clean apparently. One or two other D3 posts though that I recall have indicated a lot of back pressure/likely dirty, so my findings are better. I owned car from 15K miles and other than a handful of odd/no choice gas stations EVER, it always gets Tier 1 gas at typically high volume stations. Again, having done it on my C5 4.2 already, that A6 seemed more clogged with about 25% more miles, but also with better MPG's and less displacement (i.e. less fuel flow). Net, I could have skipped it at this point, but other data points suggest it is variable. If I reduce the risk of breakdown and diagnostics on multiple fuel pump set up--those posts often seemed prolonged and frustrating to the owner, even ones w/ a lot of experience--I'm happy.

I’ve done the same on my A8 2007 4.2 FSI last year when it had 54 K Km (33.5 K Miles). The filter is relatively inexpensive and it has pressure regulator inside. The process to replace it took about 15 min or so. Based on those reasons I decided replace it each 55 K Km (34 K Miles).

But what is interesting, my original filter was from MANN made in China. The new one is also MANN and also made in China. :)
I’ve done 10 K on it already, but it sounds like some of the original parts are made in China already.

It is not always 15 minutes job. If that single bolt goes rusty you have to cut it. Not easy underneath the car.

I’m sure it depends from the year of the car. In my case 2007 D3 it is a plastic holder and metal bolt. So, I cannot imagine the situation when you need to cut it. Even if it will be much rusted it should easy go out of there. At least in my case it was not rusted and I didn’t apply any force. It was very easy to pull it off. Also, I didn’t apply too much force when I put it back.
So, overall I think it is easy easy, unlike I had experience changing rear brakes ( see my post with description of the issue... still no one pointed where I was wrong and why it happened such way in my case. Nor anyone indicated exact steps they used to do to get it replaced)

Misha R!
BTW. I have exactly the same plastic holder as you can see on the pictures posted by MP. So, you'll be able to pull the filter always and always EASY!

Don't be too optimistic. I have just the same holder and the bolt, BUT, there is a metal nut inside that plastic and when it get stacked to the bolt (easily over time and some salty water) it will start turning inside that plastic and there is no way to get to it. In that case jigsaw is your only friend. Greasing that bolt would probably help to prevent rusting and that is actually point of this post. :)

Aha! I was not aware of that!!!!
I thought it just a plastic inside.
I'll grease it next time :)

Or...
 

anti seize compound for best of both. FWIW, mine was really easy; as I said almost was loose in terms of pressure. But then I'm an almost no salt and winter road crud coastal owner (except on Tahoe trips) in a Mediterranean climate zone.

Mishar is totally correct on this one. I just tried changing my fuel filter only to be utterly disappointed to find my bolt rusted and seized to the rear metal piece. I don't have any way off cutting the bolt so I had to give up on the task. Waste of my Sunday morning. Now I have to take to mechanic and have them mess with it. Such a terrible design.

You can cut it with hand saw blade. Not easy but works. Another way is to cut that plastic and use strap ties to fix new filter back.

Bad gas... in my Audi A8L
 

Thanks to all for contributing to this thread...

My wife filled up the 04 D3 4.2L with 93Octane at a station where a big tanker was filling up the underground storage reservoirs. That's a recipe for getting badly contaminated gas and then...

Later that same evening I was on a 50 mile drive and the car was gasping for something (gas or spark) and would not accelerate and speed dropped to no more than 20mph and eventually would stall. Would immediately start again and go for a bit then symptoms return and eve ntually stall.

Next day it ran better so I drive 11 miles to train station and it stalls. Tow it home and since then it won't run more than 30-40 seconds. Starts in an instant with no waiting after it stalls.

Replaced fuel filter, starts easily and it ran for about 3-4 minutes then it reverted back to not running more than 30-40 seconds then stalling.

I checked VCDS for DTCs and measured fuel system performance but I don't see anything to suggest what specifically is wrong. I must add that I'm not an expert on what I should be looking at so I may simply not recognize the obvious in VCDS.

Well, what say you to this info? Got any ideas?

Sounds like a bad fuel pump at first reaction
 

Let others chime in who have been through it, or search the archives, but that dying after initial start description sound like one of the tank fuel pumps to me from prior posts I've seen on the subject.

The fuel pump is bad if it runs about 30 seconds then dies. There is a good thread that we posted about this a while back. It was really "interesting" driving it to a friends shop for him to look at it with the engine only running 30 seconds at a time. My pump only lasted 90K and after it was replaced I played around a bit with the bad pump and got it to continuously spin. I think they suck up debris in the tank and it gets gummed up in the pump.

This. Ended up being a huge pain in the ass on my A6.

Incidentally I bought the very same mann filter off amazon, will be putting on the S8 whenever we get some nice weather.

Long overdue reply - I've been flying around the planet too much!

Diagnosis - Right Side Fuel Pump had been shorted out by mice who took up residence on the right side fuel pump access cover. The fuel pump wiring and fuel lines attach here.

It was obvious after removing the metal covers in the Trunk compartment. A perfect bed for mice made of insulation was packed in amongst the wiring for their comfort. What confirmed it as a bed for mice was the excrement ( mouse turds ) in their nest. Rodent threats are not discussed in any Audi repair manuals, however, Audi wire insulation is a favorite medium for rodents to sharpen their teeth. The exposed wire had evidence of rubbing on the metal cover ( front right of trunk compartment) and eventually shorted the circuit.

Steps:
1) Checked FP Relay - OK
2) Checked circuit continuity, voltage level, resistance level - OK
3) Removed pump assembly and tested pump motor - DEAD.
4) Order replacement pump from online - retailer. Audi Stealer price was $900+ Online price was $390 but had to wait 6 weeks to get it... bad timing as Bosch was short on supply to their wholesalers. This wait is not typical.
5) Test new pump motor prior to install - OK
6) Install
7) Fill tank 1/2 and run function tests and set Readiness codes (Ross-Tech)
8) Drive with smile until 1/4 tank of fuel then realize something isn't right. Realized this was 1st time fuel tank was this low since repair. Add gas - problem goes away. Hypothesis - fuel lines are routed incorrectly or suction hoses were disturbed during repair (too high in tank to suck fuel).
9) Check fuel line routing INSIDE tank and correct.
10) Close up tank
11) Test car / function tests and set readiness (Ross-Tech). Setting Readiness using Ross-Tech tests fuel supply system but doesn't test for incorrect hose routing.
12) Drive car with smile again... several tanks of fuel with no problem.

Special Note 1) When reconnecting fuel pump hoses, be sure to route the hoses correctly... per image shown in the repair manual!! The design of the hose connectors prevent incorrect connections, but do not prevent routing the lines over or under another line and that is critical. It may not seem like it would make any difference but it certainly does!

I had the manual as a reference but didn't sufficiently respect the image showing the lines connected. Consequence: was while driving in Chicago the car was stalling regularly when the fuel level dropped to about 1/4 full.

Test your repair by driving the car locally down to near empty fuel level. If no problem then you're good! Otherwise... RTFM carefully and try again.

Special Note 2) There are many other sources of failure to consider if you have fuel supply issues. Even if primary fuel pump (right side) is mechanically/electrically sound itself, the source can be elsewhere. Follow diagnostic steps carefully and use common AND uncommon sense.

If you unexpectedly discover bare wires on your fuel circuitry then consider this in your diagnosis steps.

They've had this same stupid design for awhile. I just did my A4 filter. Only it is more dificult to get at. The nut started spinning in the plastic. I used a Dremel tool to grind the head. I was trying to take it easy so as not to melt the plastic, so I could reuse the bolt hole. ...it melted through anyway. Now it's held in with tyraps.
Why didn't they use brass or stainless for this??

Pics of open fuel filter
 

I just Changed my FUEL FILTER on my 2009 A8L 4.2L at 82,700 miles on the odometer. No reason why, just did it since I was ordering other parts. Put WD 40 on the retaining triple square bolt threads and let it sit for 10 min. It came off with a snap, so there was some rust there, but luckily it came out... coated it with anti-seize when replacing.
There was very little sediment in the fuel which i drained.
I sawed open the filter (see pics). The filter element was pretty clean, with no sediment or gunk on it. The tan color was the same on the inside and outside of the element, so it is not a layer of dirt. It is nice to have it changed, but I probably could have waited till 100k miles. Anyways, I guess that's how preventative maintenance works. I replaced it with an Audi one... for something i will change 2x in the life of the car, may as well spend another $10. Hope this helps guide people as to when to change it.

I've replaced the fuel filter every 50k miles on both my 4.2 and W12. The W12 after I bought it at 54k actually was pretty clogged, could barely blow through the filter element. Cheap filter and fairly easy DIY. Too bad newer cars like my S5 have the filter in the gas tank itself.

Just done this job today on a 2009 S8. 125k miles. It was the original filter. Same issue with the ceased / rusted bolt. I used a cutting disc on a dremmel to cut the bolt out (do this before fuel lines are disconnected otherwise sparks might be a big fire risk!). Otherwise everything was exactly as described in the posts above. I am glad I did this as there was a lot of back pressure on the old filter.

Im about to do mine ~ will report back with my filter condition. Very curious to find out the condition, since mine is 175000KM ~ I highly doubt the previous owner replaced it.

First spray with Nut Buster
 

I shot mine with Nut Buster and let it sit for an hour. The clamp came loose very easily.

Anyone use PB Blaster? I've used that for several break jobs ehn trying to get the rusted rotor off of the hub and its been great.

As for the fuel filter I've added that to the list of things to look at on the S8 if I keep her long term.

I'm a big fan of PB Blaster. I didn't try either on my fuel filter nut. I just cut the bolt and replaced it with a zip tie. The fuel filter isn't going anywhere.

another big fan of PB Blaster...older folks around here swear by it. I always have a can near my tools.

I have 134k miles on my 2006 and have the filter ready. Need to get this job done asap. Good thread.

Around here PB blaster and the like are considered snake oil.

Those fuel filters are pricey little buggers at $75!

So what "mileage" are folks replacing these at? I've got an '06 with 90k.

Add me to the "not 15 min" club... Bolt was fused and had to saw it off. Tremendous pain the ass, in an uncomfortable work position (no lift for me).
Note that my car is 90% TX (no salt) and two winters in MA (limited drive time in winter though, tot of 3k miles).

Yes, i went with the Mann filter, looked identical. Original filter had a mfg date of close to 16 months before my car was built! Amazing.

No real back pressure or obstruction in my filter either, after 9 years and 95k miles.


https://cimg6.ibsrv.net/gimg/www.aud...de11edb6b0.jpg


https://cimg7.ibsrv.net/gimg/www.aud...a3bed5f291.jpg

Body saw is the key to cutting bolts like that.


https://cimg8.ibsrv.net/gimg/www.aud...690b1d507b.jpg

Hmm, not sure you have looked at the location?

No way that thing will fit!!!

:-)

Is it in an entirely different location than the 4.2? That is what I used to remove mine.

Installed
 

Using MP's picture.
Very tight in the circle, maybe 1/2" of clearance. No space for any tool at 1, and very limited space at 2.
Dremel may have worked trying to cut the head of bolt of, but likely the plastic would melt anyhow.
In hindsight - should have just chopped the plastic and used zip ties. No one will ever know except me!


https://cimg0.ibsrv.net/gimg/www.aud...ffc9937b5d.jpg

Looks the same as mine other than I have the older unit with only 2 connections. I don't remember how but I managed to get the body saw in there. Either way you got the job done and that's all that counts. I didn't put a bolt back in mine I just used a zip tie through the holes. No where for the filter to really go anyway.

I'd just get up in there with my plasma torch. Less than a minute and - boom - yer done!
https://cimg1.ibsrv.net/gimg/www.aud...d392750922.jpg

You could just plasma the filter in half and pull it out of the way. That way you have more room to cut the bolt.

:)

Plasma cut a fuel filter! Classic!

Agreed on the getting it done - I'm impressed you were able to do it.

Worst design ever.
Don't attempt this without fuel line pliers.
The M8 triple square bolt was frozen to the nut, so it just spun between the weak plastic retaining tabs, and I damaged all three fuel line connectors.
I was able to hammer the filter out of the bracket, then I cut the bracket so I could insert the new one and somewhat secure it with crossed tie wraps.
The connectors are not leaking, but will cost ~$400 if I need to replace the three lines and bracket.
___

http://www.realoem.me/Audi/RDW/A8Q/2...R/2/201/201030

https://www.ecstuning.com/b-schwaben...-pliers/p-648/
P-648 fuel line pliers $20

https://www.ecstuning.com/b-genuine-...et/4e0201505a/
4E0201505A retainer for fuel filter $32

jimellisaudiparts.com;
4E0201220A feed $135
4E0201227D return $135
4E0201218B feed to engine $95

I installed a new retainer bracket, and used Dorman 800-021 fuel line retainer clips to replace the white 5/16" (in) and black 5/16" (out) ones I had damaged removing the connectors.
The blue 3/8" (return) clip was also broken and is currently only being retained by half a clip, I've ordered Dorman 800-043 for that, but will need to cut off the double lock part to make it fit.
A good tip to unhook the connectors, already mentioned in this thread, is to move the connector towards the filter while pressing the tab in with the tool or short flat head screw driver, then sliding away and off.
___

http://www.dormanproducts.com/gsearc...0Line%2520Clip

In support of your proposition regarding extending the life of the fuel pumps, I just replaced a 10 year old filter in my 4.2 and noticed the car was quieter because I could no longer hear the fuel pumps working... I'd always though they were uncharacteristically noisy, and now I know why!