Recently replaced fuel filter...

[Divver]

Hi all, my first post here as it seems like the most relevant place for it!
I have an Audi A6 2.5 TDI V6, registered in 2002 but on a 51 plate. It's engine code AYM, 114KW, 155BHP.
I have no prior experience with fuel filter changes at all.
In my infinite wisdom I decided I'll do the fuel filter and air filter first as they'd be the quickest and easiest. I now see how stupid this was as I look back.

I clamped no pipes, I took the old O ring from my old filter and stuck it on the new one as it doesn't work and refitted the return valve. I then swapped over the inlet and outlet pipes, sucking on the inlet first to bring the diesel up til I got a mouth full and then I quickly stuck it on the new filter. I had also filled the new filter to the brim with FRESH diesel.
I had absolutely no luck starting it for anything however after a little brake cleaner was used it sprang to life. The O ring was ****** and the system was sucking in air.

Next day I acquired another filter with a brand new O ring for free, due to the first one not having one.
New filter on, bled pipes best I could with a hand primer squeezy pipe and my gob. Car ran absolutely brilliant, 41MPG at idle, responsive, sensual!
I parked the car up that night, went out next morning and it would start. Appears fuel had rolled back into the tank and left the clear inspection pipe bone dry.

So I acquired the bleeding instructions from ElsaWin.

Today I've borrowed a friend's hand held vacuum pump on a short term basis.

I clamped both pipes either side of the regulating valve on the filter, pulled the top-most pipe on the connector for the right banks of the injector pump and attached the vacuum bleeder.
I created 0.5 bar suction and pulled A LOT of air. It wouldn't even fill the container so I kept pumping away, eventually filled the container!
I clamped the vacuum pipe between container changes and filled four full containers, I pulled quite a lot of bubbles!
I then quickly removed the vacuum pump system and re-attached the return pipe.
10 seconds on the key and the engine sprang to life. Not a bubble in sight while at idle however when I give 1/4+ accelerator I can see a **** load of air travelling through the clear inspection pipe.

I've read quite a bit about the baffle housing, some procedure about connecting 12v from positive on battery to right hand terminal of fuse 28 while inlet pipe to filter is clamped to fill the baffle tank.

My question is, where's the bloody baffle tank, how do I inspect it, do I even have one or does my engine just pull with the injector pump? Is the baffle tank the reason the fuel is flowing back to the tank over night?

When I initially changed my filter my tank was just under 1/3 full.

Prior to vacuum bleeding today I made sure I had 1/2 tank.

Will changing the filter originally with less than 1/3 have buggered up the baffle system or what?

I won't know if the system is OK til tomorrow as the car is parked up now. I'm hoping vacuum bleeding it like I have will have solved everything but I don't know.

Any information and help is hugely appreciated. Thanks!

P.S. I have checked most of my pipes, hoses and connectors for leaks by spraying EasyStart on with the engine running but the engine hasn't picked up so all has seemed well there.
If it doesn't start in morning I'm going to pull return pipe from injector pump and clamp off appropriate pipes as ElsaWin instructs and then pump 1.5bar pressure into the system and check for leaks.

[ceilidhalfie]

First off, there is a fuel pump and a suction pump in the baffle chamber (of 4-wheel drive) and second suction pump in the left hand fuel tank. BUT...........'
I assume all was running fine BEFORE you changed the fuel filter - YES? If so, I would not go messing with anything around the fuel tank. If the car won't start in the morning and the clear fuel pipe is empty, the fuel has run back into the tank because there is an air leak in either the fuel filter or one (or more) of the four fuel pipes.
An electric pump between the fuel filter and the injection pump will not only quickly prime the pipes but will also cause diesel to be seen seeping out of any leak. However, simply checking the pipes, valve adapter and o-ring you should spot the problem.
For future reference, BEFORE removing old filter, clamp off the two fuel pipes NOT connected to the adapter. Next, remove clip and then adapter with the other 2 hoses still connected, and then remove the (still) clamped hoses. Fill new filter with diesel and seat. Replace with new o-ring and CAREFULLY re-attach valve adapter making sure not to crimp the o-ring. Finally attach the two clamped hoses and then remove clamps. ENGINE WILL START FIRST TIME AND CONTINUE RUNNING!
I had similar problems to you when I first changed the fuel filter on my 2002 Allroad. Having flattened the battery in trying to get lines primed, I bought the electric pump. However, the pump is now insurance - using the above procedure I have had no problems with the last 3 fuel filter changes.

[Divver]

Well the car started first time this morning, parked facing up a hill as well so the vacuum pump bleed definitely worked.

I used only a Sealey hand-held vacuum pump, pretty much identical to the VAG one listed in the process on ElsaWin.

My winning process was as follows;
1: Clamp off both pipes nearest the front of the vehicle on the fuel filter, the pipes either side of the return valve.
2: Disconnect leak off pipe from driver's side cylinder bank where it connects to the top-most nipple on the injection pump union nearest the front of the vehicle.
3: Create vacuum suction with pump between 0.5 and 1.0 bar while making sure to keep the vacuum pipe angled as vertical as possible and generally way above the injection pump.
4: Vacuum pipe begins to fill with diesel, any air locks and/or bubbles will escape and travel upward very quickly. If the vacuum pipe isn't vertical and located above the injection pump then the air bubbles will just lock up the line and diesel won't pull through.
5: Once container is full, kink or clamp the pipe between container and injection pump, unscrew the container, empty diesel into a suitable container and then re-attach vacuum pump container, remove clamp or kink from vacuum pipe between container and injection pump and then pump vacuum pump back up to between 0.5 and 1.0 bar.
6: After three containers have been filled, diesel in vacuum pipe may contain very few of the smallest of bubbles, if so then everything is OK.

Troubleshooting: If it's no better and still pulling air after stage 6 then check inlet and outlet pipes on filter for leaks, make sure jubilees are tight. Also ensure you've clamped the return pipes tight enough too. If you're able to start the engine but still see a boat load of air going through the clear inspection pipe then as I've stated previously, spraying easy start around the top of the filter and over any pipes you may suspect are leaking should make the engine rev quite violently.

I also took the time to replace the driver's side bank of leak off pipes while I was bleeding it as the old ones were covered in **** and they're hard to inspect due to braiding and build up of crud.
There's no harm in some fresh new ones as they're about £8.00 to buy for a metre length from Euro Car Parts.

P.S. I did all of the above process with half a tank of diesel, just as it makes life easier than powering fuse 28 for the stupid baffle housing crap.
Would you rather just put the diesel in so you can use it later on or would you rather bodge up a cable for powering a terminal in a fuse box or pay $80 for the official VAG cable for it, just to use it once in a blue moon