Fuel pump?

[Simon Wallwork]

Well, Ronin.

I cant afford to fcuk about here. The car chucked it as I was on the way to pick up my new born Son, and Wife from Hospital here. I'm under enormous time pressure....both baby paperwork-wise and looking after mum-wise.
Not easy getting a British child registered in rural Bulgaria.

Just hope he does it right, I really need my car right now.

[Simon Wallwork]

Sorry, Ronin- I made a mistake.
The pump is 300 Leva, not 300 Euro!

That's about 150 Euro

[MikkiJayne]

300 euro fitted is fine. 150 euro for the pump and a couple of hours labour.

I'd be in the same ballpark

[Simon Wallwork]

Ok.
Today mechanic has fitted a new pump, but he is saying that the problem is the pump was starved of fuel, and burned itself out- because of some reason I don't quite understand yet but is due to the way the tank is constructed.

Tomorrow he's going to add 20 litres of gas and run the car.
He seems to know the D2 and says, depending on some variables, either I will be able to run the car normally, or only use it from full to 1/2 full.

He's talking about putting some cleaner in to flush something or other- I honestly don't quite understand.

Is it going to need a new fuel tank?

It did stand for a year or so....although I've been using it here for about 8 months.
Fuel when it broke down was just a bit less than 1/2 a tank.

[MikkiJayne]

This is an entirely normal failure mode for these pumps. They'll fail like this on a full tank or with 5 miles to go. Starved of fuel has nothing to do with it. Neither has whatever snake oil he wants to put in it, but alas you're in his hands now so its a case of nod and smile and pay the bill.

The D2 pump is unique as it has an extra outlet on the bottom which drives suction jets to balance the two sides of the tank. The variables are whether he fitted the correct VDO pump and whether he fitted it properly. VDO properly you'll be able to use it normally. The wrong pump, or the VDO incorrectly fitted, then it'll run out of fuel at 1/4 - 1/3 tank as the suction jet won't run so it will drain the right hand side while there is still fuel in the left hand side.

Its not unheard of for the suction jet gubbins in the tank to fail, but its extremely rare. Prestige have replaced a couple of tanks for this problem, and I have yet to look at Big Red which will randomly run to empty or run out at 55 miles remaining.

I always recommend to carry a gallon of fuel after a pump replacement just in case, so fingers crossed he put the VDO pump in properly and you don't need it

[Simon Wallwork]

Thanks Mikki.
That's a very useful reply.

I quite agree. Sounds like the pump chucked it.

Also, reading your post, his patter about the pump 'running dry' is cobblers?

(If I understand you correctly, we are talking about a jet pump, working on 'motive flow' without any moving parts, but likely a seal twixt the bottom of the pump & the plumbing?)

[MikkiJayne]

There's no doubt running a fuel pump dry can kill it, but thats not the failure mode in the D2. It just wears out and stops working.

Yes, the tank balancing is a jet pump. Audi call it 'suction jet' - its basically fuel flowing through a venturi (powered by the extra outlet on the pump). There's a suction jet in each side of the tank and the flow of fuel through the venturis, plus atmospheric pressure makes them balance out the level like a siphon. When there is no flow (because of the wrong pump, or the right pump fitted without seating the outlet spigot properly) this balancing doesn't work.

[Simon Wallwork]

Got it.
Well, it used to run right down to practically empty without any trouble, so if he fits the new pump correctly all ought to be ok.

Let's see....

[Ronin]

This is the fuel system service manual, it outlines how to install/remove the pump and how to test it: http://forum.a8parts.co.uk/attachmen...8&d=1420350463

[Simon Wallwork]

Well.
Car running great, smelling a little of fuel after driving, but I guess some has been sloshed about here and there. The smell is at the off side rear.
I'll give it a day or two, see if it stops.

Guy charged me 225 Euro, which included putting 20 litres in it.

I'll carry a gallon with me now, and see what happens when it goes below where it chucked it last time- just under half full.

Looking at the old pump, which is dead, I see one large 15mm port (for engine?, and one skinny one, for jet pumps?

What a tiny fuel pump!

edit to add- Thanks Ronin!