A4 B5 1.9TDi Refuses to Fire

[Chris_J]

Quick intro: I'm quite a regular on the VW Audi scene, owning a Polo G40 as well as now this A4 TDi. Used this forum quite a bit to get handy hints, but now I've finally decided to register, so hello to all!

So, my issue with the A4 is as follows:

Was driving to work yesterday and the fuel light came on. I was planning on topping up before I got to work and it had only just hit the red. A few minutes after the light came on, I got the dreaded 'miss' then loss of power and finally the engine cut out. My immediate thoughts were that the gauge was playing up and I'd ran out of fuel, so I got a friend to come to the rescue and bring a couple gallons of fuel. Topped up, fuel light out, but she refused to start.

Towed her home and starting trying to find the problem. Whipped the fuel filter off and replaced with a new one, which I first filled with diesel; still wouldn't start. So then, I tried to narrow things down. I disconnected the inlet to the mechanical fuel pump and ran some spare tubing into a small container of diesel. When cranking, fuel is drawn up but it still doesn't fire. This was also whilst jumping off a spare battery incase I was down on cranking speed.

What else should I be checking now? The fuel that's being drawn up must be going somewhere!? Should I start stripping down the injector supplies and see if fuel is getting into the cylinders? Not sure if the whole low tank is really related, but thought I'd mention it.

What do you guys think? Thanks in advance

 

[BakPak]

Good one, this should keep us busy!

How long have you had the car, has it run low on fuel before and was there much crud in the filter?
I used to work on aircraft and cutting open fuel / oil filters was often a good way of preventing
and or finding the cause to a problem.

Chances are your fuel system just needs bleeding having just changed the filter. The fuel drawn up
could just be going back down the return line.

Without knowing the history better I would look further into what you've done since it ran low on fuel.

 

[adamss24]

If it's a manual gearbox then fill with clean diesel and tow it up the road for a few meters, it will sure fire up !

 

[MaverickTDi]

Personally I'd check your glow plugs in this order;

Visually inspect the electrical harness, making sure nothing has snapped or damaged.
Do a power supply check to the glow plugs themselves, this proves the integrity of the wiring and the glow plug relay itself.
If the above is good, change glow plugs, if bad change glow plug relay as they are known to stick open or short to ground which might explain why it seems to turn over for longer than normal before the engine actually starts. I think the relay itself provides power to the plugs to achieve optimum temperatures for a smooth and quick start, if not it will struggle and sound rough for a while.

Hope this helps?

 

[fARQUARE]

Personally I'd check your glow plugs in this order;

Visually inspect the electrical harness, making sure nothing has snapped or damaged.
Do a power supply check to the glow plugs themselves, this proves the integrity of the wiring and the glow plug relay itself.
If the above is good, change glow plugs, if bad change glow plug relay as they are known to stick open or short to ground which might explain why it seems to turn over for longer than normal before the engine actually starts. I think the relay itself provides power to the plugs to achieve optimum temperatures for a smooth and quick start, if not it will struggle and sound rough for a while.

Hope this helps?

What he said,
I had a similar issue last year where my afn wouldnt start, after taking the glow plug harnesses off I realised the connectors are not as tight as spark plug ones and some of the housings had gotten brittle amd snapped. A quick squirt of wd40 solved the problem.

Dont think the system should need bled as the ve pumps should be self bleeding...

 

[Chris_J]

Thank you very much for the responses.

BakPak: The car has a full service history up to 175k and it is now on 185k. I can't see anywhere in the documentation where the fuel filter was done, so it's likely that it hasn't been changed for a while. Regarding owners, I purchased it off my mate a few months ago, but that's as far back as I know. He says hasn't run out of fuel. I'll check the filter properly today, but I do recall it being quite dirty in there. You say the fuel could just be going back down the return, but I disconnected the return to make sure this wasn't happening and it was just blowing air out of it.

Mav/Farquare: Would a failure with the glow plugs cause the engine to cut out? I thought once it was running, it didn't require them to be operational? I'm still pretty sure that I didn't actually run out of fuel, since the light only just came on. Either way, I will certainly carry out the checks as you describe.

Cheers!

 

[MaverickTDi]

Thank you very much for the responses.

Mav/Farquare: Would a failure with the glow plugs cause the engine to cut out? I thought once it was running, it didn't require them to be operational? I'm still pretty sure that I didn't actually run out of fuel, since the light only just came on. Either way, I will certainly carry out the checks as you describe.

Cheers!

Fuel filter is an easy and cheap component to change so I would like to think it's been done at some point in it's life during servicings, to which end I'd change it anyway as you can get them for less than a tenna.

In answer to your question regarding the glow plugs causing the engine to cut out, I'll be honest, I'm not 100%.

When you attempt to start the car and turn the ignition on, does the glow plug light come on? If it doesn't then your glow plug relay 109 will need replacing as the dash indicator isn't receiving a return signal from the relay to say power is being sent to warm them up, I imagine that's how it works?

If your after an opinion, I'd replace the fuel filter for peace of mind a source a 109 glow plug relay and see what happens as there both really easy to do before you start considering more complex possibilities.

109 relay - Glow Plug Relay German Quality for VW Audi SEAT Skoda Eqv: 357911253A | eBay

 

[Chris_J]

So, after playing around today, this is what I've found:

Loosening the union on the injectors shows fuel being fed when the engine is cranking. Checked this on all four supplies and they all leak diesel.

So, I decided to check the glow plugs. Firstly the loom, all four connectors give 12v for a few seconds when the ignition is turned on. Checked the voltage across the glowplugs themselves and each one gives a different reading: 9v, 8.5v, 0.2v and 3v! I assume these are ******** then? Removed them and tried to get them to glow with the loom connected and touching the casing to ground, but nothing happens.

Weird how all four are dead though!? If this is the problem, how on earth did it happily start previously? I'll grab a new set of plugs tomorrow and see how I get on

 

[Sulli79]

If it's a manual gearbox then fill with clean diesel and tow it up the road for a few meters, it will sure fire up !

this is spot on, you say you only have air in the return, my old diesel needed a tow start after air in the fuel, did it in 2nd gear and took about hundred meters ( lots of air) then drove for a few miles, problem sorted

 

[MaverickTDi]

So, I decided to check the glow plugs. Firstly the loom, all four connectors give 12v for a few seconds when the ignition is turned on. Checked the voltage across the glowplugs themselves and each one gives a different reading: 9v, 8.5v, 0.2v and 3v! I assume these are ******** then? Removed them and tried to get them to glow with the loom connected and touching the casing to ground, but nothing happens.

Not knowing the exact voltage each glow plug should kick out, your findings do suggest that the internals of 2 of the glow plugs are goosed for sure. It would be safe to say that all glow plugs should show the same voltage, so a new set would be the obvious choice.

Fingers crossed that sorts the problem for you.

 

[fARQUARE]

Fuel filter is an easy and cheap component to change so I would like to think it's been done at some point in it's life during servicings, to which end I'd change it anyway as you can get them for less than a tenna.

In answer to your question regarding the glow plugs causing the engine to cut out, I'll be honest, I'm not 100%.

When you attempt to start the car and turn the ignition on, does the glow plug light come on? If it doesn't then your glow plug relay 109 will need replacing as the dash indicator isn't receiving a return signal from the relay to say power is being sent to warm them up, I imagine that's how it works?

If your after an opinion, I'd replace the fuel filter for peace of mind a source a 109 glow plug relay and see what happens as there both really easy to do before you start considering more complex possibilities.

109 relay - Glow Plug Relay German Quality for VW Audi SEAT Skoda Eqv: 357911253A | eBay

My afn is early 97 and does not have that relay...
Be careful trying to remove glow plugs on a cold engine, I have heard of them snapping in the past. Maybe get the bump start first, let it heat up then change the plugs.

 

[Chris_J]

I was very careful with the plugs, as I've heard similar stories too! Luckily, then came out very easily.

Replaced them with a full set and, yup, she breathes again!

Didn't half take some cranking though. Had it jumping off my G40 running on fast idle to make sure it was getting plenty of juice and it ran on 1 cylinder for quite some time. Finally, a second cylinder went and the rest is history! Man, that was difficult!

Many thanks for all the very helpful hints that got me back on the road

 

[adamss24]

I still reckon you needed to bleed the system properly, towing would have got it running straight away. The AFN is hard to kill and i have replaced glow plugs only on a handful of cars... A well set up AFN will start even without working glowplugs + they only come on in low temperatures under 5 Celsius...

 

[aragorn]

Surprised that cracking the injectors didnt bleed it enough to get it running though!

On my dads old Di transit he used to keep the appropriate spanner in the glove box to crack the injector unions off to get it started after running out of fuel.

Needed two folk though, one person to turn the key and keep the engine turning, another to crack each injector off until diesel came out. Usually it'd start after cracking and retightening two of them, sometimes three.