Hi everyone, Im just wondering if anyone could help please and has ever changed a pump in a 1999 Avant 2.5 tdi Quattro. I changed the pump last week and was running ok ish but I now have a few doubts. Im also looking for info on how the fuel tank pipes lay inside the tank. I found a diagram which looks the same as A4 piping but could be of the A6 tank pipes.

A mechanic friend took the old fuel pump fittings out as I looked on but he also took out all the bendy piping that went over into the other side of the tank (over drive shaft) as the tank has 2 sections. The old tank fuel pump was dead and made a faint ticking sound like a clock.

I have pushed the pipe over into the other side feeding it under the main inlet pipe (white inlet pipe which fuels the main chamber tank where the pump sits) and hope that its sitting at the bottom of the tank. Wether it will suck fuel from where the pipe is If I filled the tank full I'm not sure. (it was fine before). The rest of the piping is a bit all over inside the tank as its in but not layed in any order and not kinked. It was hard work to get it to stay put.

Im just wondering if the piping should all sit in the top of the tank flush as best as i can get it, bearing in mind its a nightmare connecting the (return flow) 3 pipe T piece to the underside of the green top sealant cap.

The 2 pipes which run into the otherside of the tank chamber which run parallel with the pipe that draws the fuel out of that side, I was told that the other pipe was a breather but had a long end and i dont know if it should be angled straight down into the tank of fuel or just in mid air.

The reason im needing information is that when i refitted the pump into its baynet type slot it didn't feel like it went back in properly and if it was turned too much by a few mms it would pop out and it had to be reseated, so i put it in as best as i could but was sure it had only locked on one side.

When putting the top green lid on theres a 3 way plastic T piece that connects all of the return pipes in the tank and then connects up to the green cap which is tight fitting and a pain. One of the pipe locking clips broke but it did push in and stay (i should have probably cable tied it to stop it coming out) Everything was ok until the other day when i went over a few bumps and a couple of railway crossings and whats happening now is that when i drive at 60mph the engine management light comes on, so Ive stopped and noticed that there are lots of air bubble / lack of fuel in the line from the tank as Ive seen it in the clear pipe from the fuel filter. Also if im parked on a slight downward or upward hill, after 10-15 mins stationary with the engine running the engine management light comes on because when Ive looked under bonnet, it is sucking air from the tank as this can be seen again in the clear pipe from the fuel filter.

Im hoping that its just the pump housing that has moved from its crap baynet type fitting due to running over a bump and its probably moving up and down floating in its fitting and sucking in air when the car goes fast, or it could be the pipe with no clip on come out. Even though its a return pipe im guessing it should complete an air tight vacuum. Or the new fuel pump cant keep up with sucking the fuel, as its happened again last night while I was going up and down slight hills (with engine management light flashing) on a motorway and came I off motorway and the car stalled. I got it started by free rolling and putting it into gear and it started up again, the engine management light went off and I drove home for another mile on flat roads apart from an up hill part. Its got about £10 of diesel in it but it also does it with £20 worth in, but does it more so when doing 60 mph and on bendy / upward / downward type roads.

I don't know if the pipe leading to the otherside should circulate the fuel from the main chamber to the back chamber, then back again or what but im just under the impression that it sucks the fuel from the back chamber when theres a full tank as it flows over the middle to the back rear chamber, and that the pump gives it a slight lift towards the engine but does not prime it all the way.

Ive never had a nightmare like this before, but if I run around town its fine.

I shall find out today when the lids off. Ive attached a pic of pipes. Any info appreciated. Sorry for the long post. Maybe ive answered my own questions but I need to get it sorted. I will update here with results. Thanks in advance.

Attached diagram of pipes etc.

 

After taking the lid off the top of the tank last night it would seem that the fuel pump pot had moved and was not locked so I refitted it all again, and it felt as though it did lock better this time, so I put all pipes back on and managed to stuff the T piece under the rim and seal it up. I started it up and saw the odd air bubble go through the clear pipe towards the main pump. I took it for a drive. After half a mile the glow plug light started flashing. It flashed for a bout another 1 miles worth of driving as I could see the air inside pipe and it cleared itself some minutes later.

I went to a fuel station and let it tick over and gave it some revs. Again the glowplug engine management light started to flash and then cleared itself again, so I put £10 of diesel in equalling about £18 in total. the needle went higher than it should have done but slowly went down to give a truer reading. I went for a drive for 10 miles with bendy roads and the odd slight hill and the engine management light never came on.

I stopped for an hour and restarted back another 10 miles and all was good so far so I then went and did a rerun of motorway from the other night and the road has slight up and down hills, I did 60 to 70 mph and within 7 minutes of driving 3 miles up and down the slight hilly road the engine management light came on as it was drawing in air from most probably the fuel tank?? - pipes?? when I drive faster than in town, ie 70mph.

Im getting cheesed off with it now. Im going to take it apart again on Monday just in case the fuel pump pot moved when it refitted the top cap as it is all tight with hardly any slack on pipe to pump pot plastics.

Ive looked at most other posts on the forums and they all draw a blank as the posts never get updated and finalised.

If anyone can help or knows of a fix, please reply.

 

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