1.4 Tdi Struggling to start..

PlasticMac said:
I can see how oil could pass into the fuel line, but not how it would then flow to the tank. Surely it would mix with the fuel, and end up being burnt, may upset injectors, depending on the ratio of oil to fuel.
I think the contamination in the tank is more likely to be be paraffin wax thickening and settling out.
By experience, the filters in diesel forecourt pumps need changing more often than the petrol ones.
Diesel quality can vary too. Blend varies summer to winter, with wax dose reduced in cold weather.
Mac.
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The tandem pump delivers more fuel than the injectors need along with any oil contamination. What the injectors don't use flows back to the tank taking the oil with it.

I'm thinking much the same though; that contaminated or inappropriate quality fuel has been put in the tank.
 
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 😆
 
rotifer said:
The information that @TAABVW and @Little Dog have provided us with has put weight on the side of the pump not being the source of oil in the tank. @Little Dog has more investigation work to do in the form of deconstruction of the pump to see what the hidden chambers are doing.

@TAABVW has put forwards that the injector holding o rings are causing engine oil to mix with the returning diesel fuel oil.

Hopefully someone will be able to explain how this is happening as I don't know.

The Zip file is the
SELF STUDY PROGRAMME 223
The 1.2l and 1.4l TDI engines
With Pump Injection System
Design and Function


At page 29 Audi start to talk about the injection system.

😀👍
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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.
 
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

Find many great new & used options and get the best deals for Metal Brass Straight Hose Joiner Barbed Connector Air Fuel Water Pipe Gas Tubing at the best online prices at eBay! Free delivery for many products.
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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.
Click to expand...

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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