Strange breakdown

DavidC

New Member
So...
Having driven my current 2001 A2 TDI without problem for the last 9months it broke down on Saturday and I've been unable to get it running again.

I drove the car at around 7am and returned home. I then went to leave at 10am and the car made it 100m before cutting out. Now won't start.

Starter is turning over.
Fuel guage is just over reserve.
Unclipped cambelt cover and everything is turning OK
No dash warning lights. ( Everything goes out)

I have a wireless OBD scanner and no fault codes are returned.

It seems a bit like fuel starvation. Any ideas?
 

Proghound

Admin Team
It does sound like it's a fuel thing doesn't it. My guess would be an air leak into the fuel line, preventing the tandem pump from drawing fuel from the tank. A clogged fuel filter would be another possibility, topping up might help with that.
 

dieselfan

Member
How many miles have you run since last dieselfilter change?
Did you park in a "tilted" position?
Did the engine die sudden or did it stunning a couple of times, and then die?
 

WayneoA2

Member
fuel filter has sucked up the crap at the bottom of the tank ... never run fuel low ... as this is what happens
 

DavidC

New Member
Thanks for your responses.

Car was parked on a slight incline. Nose down.
Fuel filter was changed about 3500 miles ago. I haven't had chance to jack the car up, but no evidence of diesel smell around rear of car. All running fine until this event.

I'll get some fuel and top it up. Are the fuel sender's known to become faulty? Seems odd. It implies it's stuck (if it is very low).

I always zero my trip at fill ups and the usage coincides with the reading.

Ta
 

WayneoA2

Member
Thanks for your responses.

Car was parked on a slight incline. Nose down.
Fuel filter was changed about 3500 miles ago. I haven't had chance to jack the car up, but no evidence of diesel smell around rear of car. All running fine until this event.

I'll get some fuel and top it up. Are the fuel sender's known to become faulty? Seems odd. It implies it's stuck (if it is very low).

I always zero my trip at fill ups and the usage coincides with the reading.

Ta
stick about 10 liters in it .. dare say you have sucked up crap from the bottom of the tank ... and possibly blocked the filter
 

spike

Well-Known Member
The fuel level sensor unit incorporates a shallow reservoir and the fuel supply and return lines. The reservoir is topped up via hinged flap valve and on rare occasions this can become blocked, limiting supply when the tank level gets low. Higher tank levels allow the fuel to slosh over the sides of the reservoir and restore fuel supply to the engine. Adding a couple of gallons could do the trick if that's the cause of fuel starvation
I'll try and find the pictures which will explain this much better



Cheers Spike
 
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dieselfan

Member
A2 have a quite flat plastic tank with round nice corners. Every time you turn a corner you totally alter and mix the content.
Have just emptyed and cleaned my two AMFs and they were totally clean, very unlike my boat.....
 

DavidC

New Member
Thanks again.

Firstly I always fill up as soon as I get the fuel warning, so never let it run that low.

As I said I'll get some more diesel and try that, but I'll confirm the level inside and remove the tank sender and have a look in the tank. Its been either too dark or wet to do so.

On another A2 TDI I owned, I accidentally put a couple of litres of unleaded in so had to drain the tank. I have to concur that it was pretty clean inside on that occasion.

As an aside, has anyone had an issue with the fuel line baffling causing an obstruction. In sub zero temperatures I had experienced vibration under the floor until the car warmed up and now wonder whether this is attributed to it. Just a thought.
 

Howey

Member
Fuel in tank and a tiny bit of brake cleaner sprayed into inlet should hopefully get the party started!!
 

audifan

A2OC Donor
Could be many things. Lack of fuel head pressure, pick up leaking air, filter clogged or high water content, filter connections leaking air, fuel line leaking allowing air in, tandem pump failing, injector loom failing, bad or dirty injector(s). How early is this car as the first AMF also had a pump in the tank? Obviously the first and easiest thing to try is adding more fuel. Depending on what happens after that will define next steps to take. Guess most of the components are now 20 years old.
 

Jeff Sutcliffe

A2OC Donor
Quote 'On another A2 TDI I owned, I accidentally put a couple of litres of unleaded in so had to drain the tank. I have to concur that it was pretty clean inside on that occasion.'

A couple of litres of petrol in a full tank of diesel would have done no harm. In the days before diesel included additives to prevent waxing during freezing weather, it was common to put some petrol in with the diesel to keep it fully liquid.
 

Weetank2

Member
Does the car have webasto heater

Could it have used enough in recent colder weather to alter consumption figures?
 

DavidC

New Member
So having got back from work I thought I'd have a look inside the tank. Before I did that I cranked it for 15 seconds or so but not a murmur.

Lifted rear seat and removed cover panels, unscrewed sender. Managed to dip the tank and there's still 80mm depth of fuel. There were a few dark spots of coagulated oily substance but not what I'd call dirty.
This confirmed my thoughts that the tank was not too low and it wasn't full of sh*t. Now I know the fuel guage is reading correctly.

I reassembled it and thought I'd give it another crank. After 10 seconds it spluttered in life!

So.... The only thing I did was disturb the fuel level sender unit. I haven't driven it yet as I don't want it to break down again.
I've ordered another fuel filter and I'll try it again tomorrow.
 

spike

Well-Known Member
I don't think the 80mm fuel depth would be enough to spill over into the sender 'reservoir' but moving the unit around in the tank may have disturbed the hinged flap valve and allowed some fuel in.
It's a rare fault but just filling the tank above half full would prove the theory one way or another. Either that or pull the sender unit out again and check the coarse filter screen and flap valve for debris

Cheers Spike
 

dieselfan

Member
If you have access to a vacuum pump / manual suction pump , you can connect to the tubing at the inlet of the tandem pump and the end of your AMF engine. I you in addition use a 4" long piece of clear hose you will se if you have air in the system and you can reveal if any of the components from the tank to the tandem pump do suck any air. It might sound complicated, but it is not...

When I buy a new to me, well used A2 TDI, I start with running the car until it stop. This to check gauge, and then I clean the tank.
My crank time is for AMF 15+8 and 15+10s. For wifes BHC it was 15+13s.
This can indicate that when you crank for 15s, it was not enough to start. When you then did crank 10s again , it started.

(To crank for 15s is not good for any component on the car and I do not recommend to do it, when I do diesel filter change I always use vacuum pump to avoid to crank a lot)

If your system from tank to tandem pump is OK, then it's probably good to check your tandempump.... statistically.....

I like your systematically approach, you will soon have found and fixed the problem 👍

Cheers, dieselfan
 

DavidC

New Member
Thanks for the advice Dieselfan. If there was some transparent fuel line it would have answered the fuel delivery issue quicker. .... And yes a manual vacuum pump would be handy. Ordered filter which hasn't arrived yet but drove car around the block without issue.

For the record, the tank appears to be approx 1/4 full so I don't understand how either it developed an air lock or a temporarily block to the fuel supply. I also checked around the current fuel filter and it appears bone dry. From experience, any poor sealing(leaks) within the the fuel supply leads to slow starting which I haven't been noticed.

Anyway thanks for everyone's input.
 
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