1.4 Tdi Struggling to start..

DaveySprocket said:
This afternoon I reconnected the inlet pipes to the tandem pump, and hooked up my vacuum pump to the return side, and pumped away. I got loads of air through, and some fuel. I couldn't get a clean flow of fuel without air. I had the battery charged up so I thought I would give it a go anyway, not expecting it to start, yet it sounded like it might, so I kept cranking, and away she went after about 20 seconds cranking. This was a big relief because I wasn't wanting to have to bleed the injectors!

So I returned all the piping back to normal and she started right up again, so I went for a little drive and she drove fine. When I got back I waited for a bit and then tried her again and she didn't want to start. I realised I still hadn't really resolved whether there is air in the system or not, so I put a short piece of clear pipe back in the return line and started her up again, it took a lot of cranking to start her but she fired up. I was surprised at how much pressure was in the return line, and in the clear pipe was a white froth, my connections were also leaking so I shut it down pretty quickly, but it would certainly seem like there is an air leak somewhere.

I need to get a better connection piece and some better hose clamps if I try this again, but really I need to start the hunt for the air leak, I iwll start looking around the fuel filter housing as the most likely culprit.

So I guess some kind of dubious progress has been made.. 🤔

Let the great debate about the mysterious black stuff continue. What is it, and where does it come from? Can these questions be answered, we will have to wait and see 😆
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Congratulations! Fitting suction to the return line and cranking IS bleeding the air out of the injectors. It would have started quicker if you had maintained the suction (second person) whilst cranking.
The Froth coming down the return line in the clear tube is exactly what I would expect if you are getting air in the feed line. this is the air that is bled out of the injectors
So you have found the cause of the poor/non starting. My hat lives to fight another day (ref my post#88)!

Next thing I would try is to rule out everything except the tandem pump or it's gasket. To do this I would use a new fuel pipe connected to the tandem pump fuel in and feed it fuel from a bucket/jar. Get it started by sucking on the return again. Run it for a few minutes to allow all the air out. Stop it for a few minutes and try restart. Make sure the feed tube is always in the diesel in the bucket and doesn't pop out else youll have to start all over again. If it still fails to start well the the answer is the tandem pump or gasket. If it starts well the "air in" leak is further up the feed line.
 
This is where as I have said before the clear pipe fitted to the inlet port of the tandem can help diagnose air leakage. Get the car running ensuring all connections are air tight and observe the clear pipe. If bubbles can be seen travelling towards the tandem then you have a leak between the fuel tank and the clear pipe. Now stop the car. Observe the clear pipe again and if the level of fuel drops back then the tandem is leaking or at least not air tight.

Always use the return line to vacuum fuel from the tank. By doing so you ensure the fuel line is full of fuel, the tandem if full, the injector manifold is full, the injectors bled and now the excess fuel returning through the return port.. When you disconnect the vacuum the fuel will not drop back to the tank unlike if you vacuumed through the inlet pipe.
 
DaveySprocket said:
Hello folks, I'm just getting stuck into finding out why my newly acquired A2 is having such a hard time starting, I changed the fuel filter first off, thinking it would be an easy fix, but it has made no difference at all. The problem does seem like it is fuel related, as in not enough fuel getting through.

This was the filter, so I guess it hadn't been changed for some time.
View attachment 115798

I've just done a scan and got the following message:
View attachment 115796

Probably not the main problem, but something that needs sorting anyway. The glow plug relay has been bodged up as well, so will order a new one of those.

I've looked up to find out which relay is the glow plug one, seems like it should be the one marked 614 on this photo?
View attachment 115797

I've had the battery on charge for at least 12 hours and it's not fully charged, so it might be knackered as well. I've got a tester so if it ever shows fully charged I will check it out.

Otherwise on my to do list are:

Fuel tank sender
Earth points
Tandem Pump
Crankshaft position sensor
Injector Loom
Genuine Fuel Filter

Being a bit hampered by the rain today, but I'm taking the opportunity to familiarize myself with the car and where everything is!
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good morning,
I haven't read all the posts and I apologize if I say something that has already been written.
In Italy the problem is often caused by algae that forms in the tank due to the presence of biodiesel fuel. These algae form a gelatinous mass that blocks filters, small passages, etc. The phenomenon occurs above all if the car is left stationary for a long time with the tank not completely full. There are additives to avoid algae or you can resort to the old way of putting a little petrol in the tank.
Kind regards
 
I'm with the above (comment by @audifan) but if this were my car I would drop the fuel tank and clean it out: not a massive job. Then I would clean the fuel filter housing and put a new filter in then as advised.
 
TAABVW said:
Congratulations! Fitting suction to the return line and cranking IS bleeding the air out of the injectors. It would have started quicker if you had maintained the suction (second person) whilst cranking.
The Froth coming down the return line in the clear tube is exactly what I would expect if you are getting air in the feed line. this is the air that is bled out of the injectors
So you have found the cause of the poor/non starting. My hat lives to fight another day (ref my post#88)!

Next thing I would try is to rule out everything except the tandem pump or it's gasket. To do this I would use a new fuel pipe connected to the tandem pump fuel in and feed it fuel from a bucket/jar. Get it started by sucking on the return again. Run it for a few minutes to allow all the air out. Stop it for a few minutes and try restart. Make sure the feed tube is always in the diesel in the bucket and doesn't pop out else youll have to start all over again. If it still fails to start well the the answer is the tandem pump or gasket. If it starts well the "air in" leak is further up the feed line.
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That's too funny, I bled the injectors without even knowing it :cool:

Thanks for your advice, I will definitely try the bucket idea, it would be really good to be able to start eliminating something.

I've ordered some of these so I can make better connections joining the pipes.
www.ebay.co.uk

Metal Brass Straight Hose Joiner Barbed Connector Air Fuel Water Pipe Gas Tubing | eBay

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Just be careful with those barbed connectors as you do not want to damage the internal bore of any fuel pipe as that will not help seal them.
 
Injectors don’t need bleeding, the tandem pump pumps diesel in. The cam increases injection pressure then the injection duration is controlled by the engine management system. I think it pulses twice, once for the power stroke and a second to get fuel into the soot burner. It self bleeds.
 
DaveySprocket said:
At the time I did it, it certainly seemed like a comprehensive solution, but is certainly worth revisiting just in case. I'm pretty sure I put and O ring in first, then a washer that fitted perfectly in the hole on top, then another o ring, another washer and the bolt, which probably was fully threaded.
As soon as my bundle of Fuel filters, and hose clamps arrive I will get in there again and see what is going on. Will also check the Blue one as I have not done anything with it. I maybe should just get on and buy the part that Depronman makes..

It is slightly bizarre, and also entirely wonderful how some folks who have never met, are willing to devote time and energy to resolving a random problem to help someone out and keep Audi A2's in service. All very heart warming, and much appreciated
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Over the years I e seen all sort of ‘solutions’ to the broken drain screw problem
If I’m honest none of them work successfully for any length of time. This is the main reason why I set about manufacturing the aluminium drain screw. It is identical to the Audi plastic version except the choice of material and the method of manufacture

With the issues your having and the time your investing in it, personally I would remove one of the variables and a likely cause of the issue by just replacing the drain screw with a know and proven solution

Because the 1.4 tdi does not have a tank mounted lift pump the fuel system is very susceptible to air leaks

Personally my next step after the drain screw would be the injector loom or at the very least tighten up the injector connectors

Cheers. Paul


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TAABVW said:
I have been inside the fuel sender on 8 or 9 TDI's and every one of them had a black coating inside. It is entirely possible that all of them had a bit of oil seepage past the injectors but all of them did many tens of thousands of trouble free miles afterwards. Whatever the reason for the black coating I think it is a red herring when it comes to non starting.

There is an excellent thread on here where someone took apart a tandem pump (with photos) and iirc concluded it was unlikely/impossible for oil to contaminate fuel by pump/seal failure.
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Totally agree. Also engine oil will simply mix with the diesel and effectively colour the diesel black. I’m not hearing that the fuel in the tank is black just that there is a black coating )present in every diesel tank I’ve been in to over the last 40 years)


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depronman said:
Over the years I e seen all sort of ‘solutions’ to the broken drain screw problem
If I’m honest none of them work successfully for any length of time. This is the main reason why I set about manufacturing the aluminium drain screw. It is identical to the Audi plastic version except the choice of material and the method of manufacture

With the issues your having and the time your investing in it, personally I would remove one of the variables and a likely cause of the issue by just replacing the drain screw with a know and proven solution

Because the 1.4 tdi does not have a tank mounted lift pump the fuel system is very susceptible to air leaks

Personally my next step after the drain screw would be the injector loom or at the very least tighten up the injector connectors

Cheers. Paul


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Thanks for the advice Paul, I'll PM you to place my order. :)
 
rotifer said:
Afaik,
Diesel mixed with the oil flows back to the tank via leak off from the injectors. I think, I'm not sure, the injectors receive an abundant supply of fuel from the pump and they can't use it all so send some of it back.
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Spot on. 95% of fuel is returned to the tank via the fuel cooler


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TAABVW said:
It was Goddas who suggested that oil might be getting into the fuel tank through injector seals. I was just not disagreeing with this possibility since i don't know.

I am not convinced the black coating is oil at all. It could be a light dose of the bug or just residue from thousands of litres of (not perfectly clean) diesel. Either way, other than causing a physical blockage, I'm pretty certain it is a red herring for the non starting problem at hand.

If it is oil in the fuel tank then the concentration in the fuel would be tiny and not a problem else it would quickly colour the fuel. The engine would run happily on 50% engine oil.

I would also like to clarify that I would not rule out the tandem pump or it's gasket as the cause of non/poor starting until zero air in the fuel return has been established.
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Could not agree more


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Little Dog said:
Injectors don’t need bleeding, the tandem pump pumps diesel in. The cam increases injection pressure then the injection duration is controlled by the engine management system. I think it pulses twice, once for the power stroke and a second to get fuel into the soot burner. It self bleeds.
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True when the engine is running. False if you have air in the injectors before it starts.
 
depronman said:
Spot on. 95% of fuel is returned to the tank via the fuel cooler
I was very surprised how warm the diesel cooler gets-at a recent MOT test whilst car was in the air I ducked underneath to have a look around and placed my hand on the cooler-it was pretty warm! I presume it’s the heat from the cylinder head transferring into the diesel as it circulates.

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Yes mainly heat soak from the head into the tandem pump then into the diesel
Ideally you want the diesel as cold as possible for best power and economy hence the fuel cooler is in place on the return to the tank

Paul


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Well reflecting back on all this, I am suspecting that I quite possibly fixed the original fault by sorting the sender, and inadvertently introduced a different fault, by not properly sorting the bleed valve. Time may tell..

I'm away for a mini weekend break to Dumfires and Galloway, but I have ordered various bits n bobs so that I can get back to it better equiped next week.

I just wanted to say a huge thank you to everyone for their patience, advice, and general input on this thread, it really is appreciated and I have learnt a huge amount already. Maybe more importantly, it is so refreshing that everyone is so nice to each other. I had to walk away from another forum because even though the levels of help and advice were quite amazing, the levels of racism, misogyny and xenophobia were truly shocking.

Back in the day they used to say only nice people drive Saabs, maybe only nice people drive Audi A2's ;)
 
I think it is true, only nice people drive A2's. Pleased you are sorted but I would also be looking to eliminate that gunk in the tank. I'm reasonably confident it is not oil. Dirty oil and clean diesel combine to make dirty diesel. The oil does not separate out and is not attracted to plastic items.

IMG_1082.JPG


I got my own A2 problems to sort; Little Dog is stubbornly refusing to start :rolleyes:
 
Well it's been a while since I bathed in diesel, and my new drain plug arrived from Depronman today, so I had to fight off a bout of lethargy and go and play with this car again.

The Febi Bilstein Filters I got from ebay included all the O rings, so I put the two on the new drain plug and fitted it to the cap.
IMG_20240321_131856_HDR.jpgIMG_20240321_144616_HDR.jpg
With Paul's aluminium plug you don't have to remove it to do up the cap, which is way better than the Audi design.

With the filter back together, I bled the system from the return pipe in the hope that the starting problems I'd been having would be all gone :rolleyes: No such luck unfortunately, she really didn't want to start at all now. :mad:

Next step was to test the tandem pump itself, so I hooked up a tank of diesel to the feed, and connected the return to an empty tank.
IMG_20240321_160205_HDR.jpg
I've got much better hose clamps now, so I was confident of good connections. I tried bleeding the fuel through again with my vacuum pump, but even set up like this I couldn't rid the return line of air, or suck any significant amount of fuel through the feed pipe. When cranking the engine I could see a bit of fuel move up the feed pipe with each turn of the engine, but as soon as I stopped it returned back to the tank.

Despite lot's of bleeding and cranking, still nothing at all, so it's looking like it must be the tandem pump, it seems to have died altogether. :eek:

Before I go on the hunt for a new pump, I will wait and see if any of you clever folks on here have spotted some amateur mistake that I am making here, I would hate to buy one and it not be the actualy fault 🤔.
 
Some might not agree with me here and I was very reluctant to do this but I got some easy start yesterday and splitting the air intake near the MAF sensor I gave it a couple of small burst, I quickly grabbed the key and turned it, she fired up instantly and kept running with no problem.
I'm assuming that there must have been fuel in the tandem pump and feed lines.
I left it running for around 20 minutes, turned it off and left it for an hour, returning back I turned the key and she started up but did take around 7 cranks.
This afternoon I again turned the key and she started again but with only 4 cranks.
There is still a few bubbles in the clear tubing feeding the pump so there is still air entering the system but at least now I know the glow plugs are ok, the injectors are ok, and th e injector loom is ok.
Plus the cam sensor and crank sensor.
I've even taken it out for a spin for the first time in months around the small estate where I live.
 
DaveySprocket said:
Well it's been a while since I bathed in diesel, and my new drain plug arrived from Depronman today, so I had to fight off a bout of lethargy and go and play with this car again.

The Febi Bilstein Filters I got from ebay included all the O rings, so I put the two on the new drain plug and fitted it to the cap.
View attachment 121066View attachment 121065
With Paul's aluminium plug you don't have to remove it to do up the cap, which is way better than the Audi design.

With the filter back together, I bled the system from the return pipe in the hope that the starting problems I'd been having would be all gone :rolleyes: No such luck unfortunately, she really didn't want to start at all now. :mad:

Next step was to test the tandem pump itself, so I hooked up a tank of diesel to the feed, and connected the return to an empty tank.
View attachment 121067
I've got much better hose clamps now, so I was confident of good connections. I tried bleeding the fuel through again with my vacuum pump, but even set up like this I couldn't rid the return line of air, or suck any significant amount of fuel through the feed pipe. When cranking the engine I could see a bit of fuel move up the feed pipe with each turn of the engine, but as soon as I stopped it returned back to the tank.

Despite lot's of bleeding and cranking, still nothing at all, so it's looking like it must be the tandem pump, it seems to have died altogether. :eek:

Before I go on the hunt for a new pump, I will wait and see if any of you clever folks on here have spotted some amateur mistake that I am making here, I would hate to buy one and it not be the actualy fault 🤔.
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Provided you are absolutely certain the rubber fuel feed pipe to the tandem pump is air tight (and to be honest the only way I think you can be certain is to replace it with a new supple fuel pipe) then I think your diagnosis is correct. All I would add is, I would possible try a new gasket on the old tandem pump before replacing the actual pump. When the pump gasket leaks there is usually some sign of diesel leakage underneath the tandem pump. The gaskets are relatively inexpensive and quite easy to fit.

Well done for persevering and narrowing down the problem. You now know that the problem is air in the fuel and you have pretty much ruled out any leaks further up the fuel line.

Maybe a little positive pressure on the feed line (blow down it with you finger over the return?!) might elicit and external diesel leak???
 
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