Fuel Filter housing construction and flow paths

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
The attached PDF shows a destructive examination of a filter housing that is common to CJAA, CBEA, and early BRM's.

http://pics.tdiclub.com/data/517/Fuel_Filter_housing_construction_and_flow_paths.pdf

I learned several things:
1) The screw on top of the housing is a very poor vent path. If you try to vent out of here, a lot of air is trapped in the housing. This is a tube that is only open on the very bottom of the housing. It is intended for you to stick a tiny (1/8" or 3.2 mm O.D.) hose down this and pull water out with a syringe or vacuum pump. Alternatively you could seal with a tapered rubber plug at the top of the housing and pull from there, since the interior passageway is sealed with o-rings. I would do this twice per year, or every 5k.
2) The housing has two areas that can trap water, one at the very bottom of the housing discussed above, and the second is a plenum in the bottom of the center black post. The only way to get water out of this area is to dismount the filter housing and turn it upside down. The water would run out of the fuel inlet port on top of the center post. I would do this every 20 k or filter replacement.
3) Even at room temperature the recirc flow (return flow from the HPFP and fuel rail) is free to enter the outer chamber of the filter and mix with incoming fuel from the tank. There appears to be no thermostatic shutoff on this flow path as there used to be with the A4 fuel filter.
4) After opening the fuel system, such as replacing a filter, you should use VCDS, Engine module, basic settings, 035, to run the fuel lift and auxiliary (boost) fuel pump for 60 seconds, three times. Start engine, run for a few minutes at idle and moderate speeds and check for leaks. Clear DTC memory, Then take it for a drive of at least 12 miles (20 km), going to full throttle at least once. Recheck for leaks, check and clear DTC. If it goes into the limp home mode, stop and clear DTC. Repeat road test until the system is fully bled and no DTC's are set.
 
Last edited:

PowerDawg

Active member
Joined
Aug 8, 2009
Location
TX
TDI
09 Jetta TDI Sedan
Very Interesting

I wonder why this "Bleed Screw" was never identified/clarified before? It seems very logical for any diesel filter/separator to have a method to drain water. Syringe with tube, hmm I am gonna try this sometime soon. I did check for "Metal" last week and had none on top.

Could this possibly be how the dealer checks for "water/metal contamination" when denying warranty coverage?
 

Osage Orange

Veteran Member
Joined
Nov 21, 2008
Location
Lewistown IL
TDI
2009 Jetta *sold*
PowerDawg said:
I wonder why this "Bleed Screw" was never identified/clarified before? It seems very logical for any diesel filter/separator to have a method to drain water. Syringe with tube, hmm I am gonna try this sometime soon. I did check for "Metal" last week and had none on top.

Could this possibly be how the dealer checks for "water/metal contamination" when denying warranty coverage?
I wouldnt doubt this as being their retard logic. Anything other than an independent lab analysis test result is bogus assumption.
 

El Dobro

Top Post Dawg
Joined
Feb 21, 2006
Location
NJ
TDI
2017 Bolt EV Premier, 2023 Bolt EUV Premier
I haven't picked up an '09 Bentley yet, but the '06 version tells you to remove approx. 100ml of diesel fuel through the plug hole using tool VAS 5226.
 

PowerDawg

Active member
Joined
Aug 8, 2009
Location
TX
TDI
09 Jetta TDI Sedan
El Dobro said:
I haven't picked up an '09 Bentley yet, but the '06 version tells you to remove approx. 100ml of diesel fuel through the plug hole using tool VAS 5226.
I am just curious, does your Bentley manual specify a purpose for doing this? ie removing water accumulation, bleeding/purging?
 

Pelican18TQA4

Veteran Member
Joined
Sep 7, 2002
Location
Philadelphia, PA
TDI
'13 Jetta Hybrid
I never once had water in my BEW fuel filter. Also, I thought that VW removed it from the CBEAs? The service schedule doesn't stipulate a drain interval for it. Also, what engine is the CJAA?
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
I never have water either in my 2005 BEW, but I do take steps to ensure the water is removed.
I use Power Service Diesel Fuel Supplement religiously.
I have checked my tank twice, and fuel filter several times. No water.
 

El Dobro

Top Post Dawg
Joined
Feb 21, 2006
Location
NJ
TDI
2017 Bolt EV Premier, 2023 Bolt EUV Premier
PowerDawg said:
I am just curious, does your Bentley manual specify a purpose for doing this? ie removing water accumulation, bleeding/purging?
It was to remove any water that accumulated at the bottom of the canister. I was told that the original fuel filter cartridge was made out of a material that would seperate the water from the fuel. Later on, VW changed the cartridge and eliminated the bleed screw. The new cartridge was interchangeable with the old but was no longer a coalescer.
 

Pelican18TQA4

Veteran Member
Joined
Sep 7, 2002
Location
Philadelphia, PA
TDI
'13 Jetta Hybrid
DanG144 said:
My wife's 2010 Jetta is a CJAA, it appears identical to a CBEA. I have yet to discern a difference.
Interesting that VW changed the letter designation for the '10 engine. If I recall correctly, all '99.5-'04 MkIVs were ALHs, all '05-'06 Golfs and Beetles were BRMs, and all '05.6-'06 Jettas were BRMs. These letter designations were because of engine changes. Strange that the engine designation would change for '10 when the engine hasn't changed at all from the '09 (that we know of, of course).
 

tdiatlast

Top Post Dawg
Joined
Jan 21, 2009
Location
Fort Worth, Texas
TDI
2009 Sportwagen (boughtback); 2014 Passat TDI SEL (boughtback)
Bentley manual states all post 2006 filter canisters DO NOT havethe bleed screw, and has photos showing the same. It also states that no bleeding/purging is necessary.

Both my TDIs have the bleed screw. Curious.
 

KirbDog

Active member
Joined
Jul 7, 2009
Location
Pittsburgh, PA
TDI
2009 Jetta Sedan TDI
On a related note: priming......

1) The screw on top of the housing is a very poor vent path.
What is the vent path for these filters?

Just last wekend I performed my first (VW) oil change and fuel filter change. I removed virtually all of the fuel from the canister bowl with a turkey baster, changed out the filter element, buttoned-up the canister, and attempted to prime the filter by way of the commonly talked-about KOEO method. I cycled the key maybe three times......and just for kicks.....I opened the canister back up to see if fuel was actually filling inside the bowl.

It was not. :confused:

I went through the process again, and to no avail..... After a lot of hemming and hawing, I decided to start the engine. Well, it started and ran with no problem....:eek:

Don't know how the air got out......
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
Cycling the key on and off did not work for me, either on the 2010. (It works great on the PD's.)

It seemed as if it ran the first time, then no more. The filter was no more than 30% full. I filled the filter on the dirty side, until it was full, filling and venting from the same hole.

I am still working to figure out a good method with the lift pump. Perhaps we need to remove the key between each cycle? I intend to try this next time I have a chance.
 

Fencemaker

Veteran Member
Joined
May 12, 2006
Location
Washington, PA (SW PA)
TDI
2006 Jetta TDI 5sp; 2009 JSW TDI 6sp
Curious that you didn't get a prime. With my wife's 09, I just did key on, key off about 3-5 times and it started right up! Of course, I may have removed the key each time, I just don't remember.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
I am pretty sure it would have started and run. I did not want to try it.

I wanted no air to be sent to the system. So I manually filled it before I ever hit start, ensuring to fill from the dirty side of the filter, so no fuel every bypassed the filter.

The HPFP is too expensive to take chances with.

Since the Bentley is seemingly wrong about the style of filter installed, I did not feel as if I could blindly trust it.
 

KirbDog

Active member
Joined
Jul 7, 2009
Location
Pittsburgh, PA
TDI
2009 Jetta Sedan TDI
Curious that you didn't get a prime. With my wife's 09, I just did key on, key off about 3-5 times and it started right up! Of course, I may have removed the key each time, I just don't remember.
As I mentioned, mine started up just fine as well (and I'm talkin' NO extended crank time.....NO coughing and sputtering), but there was no indication that a prime took place........which begs the question: Is a prime even necessary? One would think it is necessary, but maybe there's some sort of hydro-mechanical trickery going on......

I forgot to mention, that after I did start it, I opened the canister one more time (oi!) just to check........ Sure enough there was fuel (as typical).

The HPFP is too expensive to take chances with.
Hence my "hemming and hawing"......I don't blame you for erring on the side of caution!

the Bentley is seemingly wrong about the style of filter installed, I did not feel as if I could blindly trust it.
Tell me about it! :rolleyes:
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
tdiatlast said:
DanG144,
Great post.
Any idea of the diameter of the tubing needed for the extraction?
Thanks.

It looks as if 1/8" (3.2mm) OD tubing is about the largest that will fit into the hole.

Another alternative is to seal around the lip of the screw hole, say with a tapered rubber plug, since there are effective seals on the assembly all the way to the bottom of the assembly.

We have typically used IV tubing from trashed (but never used) hospital stores, and adapted it up to a MityVac. This is considerably smaller than 1/8".

I would check the water removal tube by inserting tubing about twice per year, at least every 5 k miles, and when I changed the filter, I would unbolt the filter housing and turn it upsidedown for 10 minutes to allow the other internal water trap to drain. The plenum inside the central tube that otherwise is impossible to drain.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
Priming fuel system on CBEA or CJAA with VCDS

I was doing a little homework tonight and found how to prime the fuel system in my Bentley's.

I updated post #1 with this info.

You have to use VCDS or a similar tool.

After opening the fuel system, such as replacing a filter, you should use VCDS, Engine module, basic settings, 035, to run the fuel lift and auxiliary (boost) fuel pump for 60 seconds, three times.
Start engine, run for a few minutes at idle and moderate speeds and check for leaks.
Clear DTC memory, Then take it for a drive of at least 12 miles (20 km), going to full throttle at least once.
Recheck for leaks, check and clear DTC.
If it goes into the limp home mode, stop and clear DTC.
Repeat road test until the system is fully bled and no DTC's are set.

Note that the Bentley still has a bogus note (or at least one that does not apply to our cars) saying the fuel pumps come on when the door is opened or the key is inserted. It does not do this on any TDI I have ever looked at.
 

El Dobro

Top Post Dawg
Joined
Feb 21, 2006
Location
NJ
TDI
2017 Bolt EV Premier, 2023 Bolt EUV Premier
Someone on the site said they heard the pump cycle when they opened the door in a quiet garage.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
I never have. My garage is quiet.

The pumps running is very noticeable. Not real quiet like the old simple lift pump. And you can distinctly hear both pumps run.
 

PowerDawg

Active member
Joined
Aug 8, 2009
Location
TX
TDI
09 Jetta TDI Sedan
Update

PowerDawg said:
I wonder why this "Bleed Screw" was never identified/clarified before? It seems very logical for any diesel filter/separator to have a method to drain water. Syringe with tube, hmm I am gonna try this sometime soon. I did check for "Metal" last week and had none on top.

Could this possibly be how the dealer checks for "water/metal contamination" when denying warranty coverage?
I got around to checking this out today. I used a small handpump with a hose that fit OVER the fitting after removing the screw. I pulled out about 400ml in a clean mason jar. No water or any other contamination that I could see. Just nice clean diesel fuel.

I started it up and ran it for a miniute and reved it up (ran fine).

I am wondering if I sucked it all out of the filter housing this way (emptying it) or was the handpump also pulling fuel from the supply line to keep the filter full??
 

Bob S.

Top Post Dawg
Joined
Aug 17, 2006
Location
Central MD.
TDI
A B4V, some ALHs & BRMs
Dan; Good stuff. Thanks. I am till trying to get a grip on those passages between the filtered & unfiltered area at the bottom. What purpose do they serve? It would appear that they are intentional.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
Bob,
I think I know the ones you are talking about. I need to number my pages in the PDF, and make a few updates. But this is on the last page.

Looking at the bottom of the fuel canister, there are purposefully installed passages that allow free flow of fluids into the center area of the assembly mounting flange.

The mounting flange would other wise block the free flow of water from around it into that center cup. The center cup area (interior of the flange) is where the water removal passage pulls from. The intent is to allow water to pool in the middle and thus be removed periodically via the water removal port(number 3, green tie) - and to let you get most of it out.

Dan
 

Ski in NC

Top Post Dawg
Joined
Jul 7, 2008
Location
Wilmington, NC USA
TDI
2001 Jetta ALH 5sp stock
Looks like that bleed screw, if you crack it open with engine running will spit out what is on the bottom of the housing. So if water is present, that's what will come out. Probably messy.

So I guess that's why there is no water drain on the bottom. It's on the top.
 
Top