2005 2.5L R5 TDi cold start problem

BenEadir

Hi Guys,

My (up until now) trusty and much loved 2005 2.5L VW Touareg R5 TDi has over the last 5-6 months developed an intermittent cold start problem. In the beginning it was taking a little longer to fire up, then after a few weeks when it fired up it it sounded like it was misfiring for the first few seconds i.e. it was only firing at half the usual RPM's for 5-10 seconds but then warmed up to normal RPM's and off it went. This problem occurred about 25% of the time and always at the first start of the day, never later on in the day. I had the car serviced and had new glow plugs fitted but the problem didn't go away.

Over the last few days the problem has developed further to the point where the car doesn't fire up at all for the fist 2 or 3 attempted starts but eventually it does fire up.

Here is a one minute video of my first start today. It was around noon and it was 7.5C outside so not a 'cold' day. You will see that the engine is being turned no problem by the battery but it takes three attempts to get it to fire.

View My Video

I'm concerned that the problem is related to the injectors and that means big €'s to fix which I don't want to put into what is now a 9 year old car.

All thoughts, suggestions etc very much appreciated.

Ben

Interslice

Could be the lift pump in the tank. Is it worse when fuel is low? Vagcom scan would be handy.

BenEadir

Interslice wrote: »

Could be the lift pump in the tank. Is it worse when fuel is low? Vagcom scan would be handy.

Hi Interslice,

Haven't noticed it being worse with low fuel. Will fill the tank in the next few days and see if things improve while it's near full.

I assume I can only get a Vagcom scan from the garage I use?

Ben

Interslice

BenThere wrote: »

Hi Interslice,

Haven't noticed it being worse with low fuel. Will fill the tank in the next few days and see if things improve while it's near full.

I assume I can only get a Vagcom scan from the garage I use?

Ben

Where you based? someone here might be able to sort you out.

Your starter seems very weak in the video. Could be poor voltage from the battery. Is it an old batery?

Air getting into the fuel lines though the fuel filter valves, lift pump, clogged fuel filter and battery condition would be the first things I'd check before going any further anyway.

HTH.

BenEadir

Interslice wrote: »

Where you based? someone here might be able to sort you out.

I'm based in Stillorgan/Sandyford area.

Interslice wrote: »

Your starter seems very weak in the video. Could be poor voltage from the battery. Is it an old batery?

The battery voltage seems to be a consistent 14v per the dashboard meter. There's never any weakness apparent to me. Can't remember if the battery is 2 or 3 years old but thereabouts. The sound in the video isn't great as I think I had my finger over the microphone a bit, that might be why you think the starter is weak?

Interslice wrote: »

Air getting into the fuel lines though the fuel filter valves, lift pump, clogged fuel filter and battery condition would be the first things I'd check before going any further anyway.

HTH.

That's very helpful Interslice. I'm beginning to think the Lift pump is the problem as the others should (I'm guessing) occur equally throughout the day whereas the problem I'm having only occurs at the first start of the day when the car has been standing for 10-12 hours. Could the lift pump be draining slowly overnight resulting in the starting problem first thing in the morning? Once if gets going there is never enough time between starts during the day to completely drain?

Useful/useless hypothesis?

Ben

Interslice

Appears the non-return valve on them is on the lift pump rather than the filter like the older VW's. One suggestion was to clamp the fuel lines over night and see if that valve is at fault.

dieselbug

Sounds like an airlock as it starts first time then cuts out.

Starts again after extended cranking, cranking speed sounds good, so starter would appear ok.

BenEadir

Thanks lads, your input is helping me to identify/isolate the problem.

Two more interesting (to me anyway) videos this morning. The first one one again shows the cold start problem. It takes three attempts to get it to fire and on the last one it seems something finally clears or clicks allowing the engine to start. To me the battery is doing a good job and it sounds like everything is turning (cranking?) properly.

View My Video

The second video is 20 minutes later after the school run. I parked up, switched off and waited a couple of minutes before starting the engine. I started it three times and you can see that on all three occasions it fired up first time no problem and it will continue to do so all day/evening but tomorrow morning the problem will be back.

View My Video

The idea of an air lock developing over night (or at anytime the car isn't being used for an extended period of time) seems logical to me.

How do I explain this to my garage so that they can fix it straight away without going down any incorrect roads or taking hours to figure it out?

Interslice

http://vwpress.files.wordpress.com/2012/01/ssp-305-e.pdf

Page 20/21 gives an overview of the fuel system. Air could be getting in from a few places. I think it would really need a specialist mechanic to diagnose the problem. Could be worth sending George Dalton on here a PM too see what he thinks.

For what it's worth if I were DIYing it I'd run a vcds scan for fault codes and check the fuel pressure on cranking. If there were no codes for a crank sensor or the like and fuel pressure was low I'd try a new fuel filter and a non return valve between that and the mechanical pump. Then test or replace the lift pump. If none of that worked I'd start to be worried.