Felix.

Audi A4 2.5 TDi V6

From my earlier post, I'm now satisfied that the leak was diesel and not engine oil.

Anyway, can’t see where the leak was from, but it seems to have collected in the 'V' of the engine behind the pump.

No obvious leaks from the pump, but the car still won't start.....

Cleaned it all down, charged the battery up. When you try and start it, you can see fuel moving along the clear pipe into the pump. Removing the metal injector pipes going to the injectors shows that fuel is coming out when the engine is turned.

Checked the filter which is not blocked and tried to start it by missing out the filter al together and placed the end of the pipe straight into a jar of clean fuel. No joy and the pump didn't seem to be sucking anything out of the jar.

Wondered if the clear pipe was blocked in some way between the filter and the pump, so took that off and blew it through and it was fine.

Now, I have run out of ideas other than tow it to a garage with a spare arm & leg. How much pressure should the pump be running at and is the pump the kind of thing that either works or doesn't

I have posted this on the Audi forums, but I thought I would try here as well

Any ideas......

fatscoobfella1

iTrader: (1)

The pump is a common failure on the 2.5V6..

And yes,the pump drops internal pressure and when it drops below injector pressure the car wont start.

Wooffy

Check the spill return pipes from the injectors as they crack and leak when they get old which causes the fuel to run back enough to prevent it from starting. If it is them then replace them and bleed the fuel system and it should start.

Felix.

Just a thought then.....

Could it be the return pipes are leaking - In that way, air will get into the system. The return pipes pass back through the filter so I assume that the air can now enter into the feed lines. Hence eventually, there will be too much air for the car to cope with and it stops.

Wooffy

Pretty much, yes.

The Zohan

+1

Jamz3k

Just buy an Alfa and be done with it I say........german reliability PAH!

Felix.

I’m beginning to agree – or a pushbike seems a viable option at the moment.

Air still getting into the system although it almost started a few times. I’m beginning to think that by replacing the fuel filter I have introduced more air. In that the feed pipe to the filter drains back to the tank when I took it off and I can’t fill the pipe before I put it back on the filter without it draining back to the tank again and introducing air.

If I get a hand primer and put it the other side of the filter (the outlet pipe) and prime it, then once the diesel has filled the pipe from the tank and fills the filter, then it can’t return and hence no more air.

Is this a good theory.............

The pump seems ok, it pulls the diesel through but stops when it hits the air pocket..

skinner

If its got a small air leak from a pump seal it wont start. Did you cause the fault or wont it start because of a air lock.Ihavent seen your earler post.

fatscoobfella1

iTrader: (1)

Have a read here....

Anything sound familiar ??

http://www.dieselpumprepairs.com/#/v...res/4533030669

Felix.

The initial fault (I believe) is one of the return hoses from the injector was split, leaked diesel out over time (which I didn’t see cause it was rainy) and the car stopped. I suspect that air has slowly got into the system by this leak and as the return pipes passes through the filter, air has got into the inlet system.

And now I probably made it a bit worse by tinkering

I assume that this was the only leak as the pump itself was totally dry all around it and everything else seems tight.

fatscoobfella1

iTrader: (1)

So....

Has the car still got a diesel leak ??

skinner

If you have sorted your leak there should be nothing to stop it starting apart from air in the system.If i was you id fill the filter housing with fuel and let the pump run by turning ignition on.Id then crack the injector pipes off and crank the engine over to get the air out.Nip them back up and try starting it.Be carefull to not burn your starter motor out by getting it to hot.If that fails you may have to toe start it if there is no other faults that will get it going.

Wooffy

The VP pump fitted to the audi isn't strong enough to draw fuel without being bled first. Just grap a cheap hand primer and put it into the supply pipe from the filter to the pump and get some fuel up to the pump. Once you've got it bled crank the engine over whilst still pumping the primer till it starts. Let it warm up, switch off and quickly remove the primer, fire the engine up and run it at around 2-3000 rpm as soon as it starts so it will quickly overcome the small amount of air you just introduced removing the primer.

fatscoobfella1

iTrader: (1)

Thought the Audi had a pre supply pump ?

Felix.

Cheers guys, i will give it a go

Happy New Year by the way

Still no replies on the Audi threads - which shows the power of scoobynet

Wooffy

It doesn't

The Zohan

modern Diesels run at very high pressure - some 20-40bar (VW PD Pump Deuce engines run 40 bar from memory) depending. If the pump is not delivering the correct pressure it can and does damage the injectors and the car will not start.

read here - http://www.ecutesting.com/audi_a4_a6...esel__pum.html had a mate who's pump packed in on his a6 2.4 (this website echo's FSF's comments/posts).

In addition if the pump has run dry(in your case fuel leak/airlock) it could be fcuked - the diesel also lubes the pump.

speak to this lot (in the link) as this where where my mate got his sorted.

fatscoobfella1

iTrader: (1)

Is it just a transfer pump thats in the tank then ??

Wooffy

It doesn't have one at all. The 2.5 tdi is fitted with the bosch vp series pump similar to the vp44 fitted to the vauxhall 2.0 dtl and dth engines (albeit a six cylinder variant) They draw the fuel via the pump itself but aren't that strong so rely heavily on the system being bled and airlock free.

fatscoobfella1

iTrader: (1)

Well the one i did a couple of months ago definately had "something" in the tank...

It was accessed through a panel in the boot,...

Wooffy

Fuel guage sender unit,

fatscoobfella1

iTrader: (1)

Yep,that was integral within the unit.....

Car was an 02,dont know if that makes a difference at all.

Felix.

Well armed with my one 'DIY' one way valve pressure pump (and a hang over) attempted to draw the fuel through the filter to rid the thing of air.

Spent a good while pulling more air through the filter, so tried pulling from the pipe itself from the tank..... still nothing.

Then tried to pull straight from the tank... nothing

I think the sender unit is buggered....... I will get there eventually.

I dont think the pump has ever run totally dry, as there is fuel in the pipe - but the air behind it is possibly effecting it too much

fatscoobfella1

iTrader: (1)

It shouldnt take that amount of bleeding...

You either have a great big hole in the fuel system or the pump is wankered.

Felix.

I'm fairly sure its the sender unit/lift pump in the tank, put a live feed to it, you can hear it struggling away, coughing and spluttering. Its very hard to get it out though, so it pains me, but I may have to take it to a garage bloke

fatscoobfella1

iTrader: (1)

Woofy says there is no lift pump in the tank...

So if thats correct,and i think it is...Then your going in the wrong direction.

The Zohan

The fuel pump s a common well known fault and i understand the op wanting to explore other avenues prior to condemning the pump and i do hope it is a simple and cheap fix but it is much more likely to be the pump at fault if not the original problem but now compounded by a lack of derv and knackered internals...