D3 Intermittent Start Fault
 

I have a 2005 D3 3.0 TDI Quattro with an intermittent fault since May. Car will start but sometimes there's a lag between turning the key and starter kicking in and when out and about after a couple of stops will not start. Turn the key hear relays clicking but starter does not engage. Leave it a while (can be 30 mins - 2 hours) it'll start again. My garage has replaced starter ecu, ignition switch, starter motor. I've replaced engine coolant sensor and starter relays. Audi re-coded ecu, replaced and coded new battery. Audi had the car for two weeks started 4/5 times each day but never drove it so fault never occurred. Any help and ideas will be gratefully received.

Can you post a full VCDS scan??

Thanks for the reply but I don't have VCDS information. My garage uses a third party for in depth diagnostics who wants to extract all fault codes for subsequent analysis. Sorry I can't be clearer than that.

Is it worse when it's been raining? My 2003 D3 had an issue with water ingress when I got it, which caused issues with starting.

Could be as simple as an earth strap on the starter or even the battery.
When you say "replaced", are they new parts or from a breakers ?
Could be a suspect replacement part.
Before spending anymore on parts, it might be more prudent to get the car to a decent auto-electrician.

Well, I would say get the full scan done by one of the local to you forum memeber (look in the vag com register thread) and post the results so we can have a look.
It looks like they may be using basic scanner where they cant see the whole scan so they just keep changing parts using the lottery strategy.
With A8s in most cases you need to look at the entire scan before making the call what to change first.
For example an ABS fault can be caused by a faulty steering angle sensor and I've seen people having ABS pumps changed.
Battery fault caused by faulty battery ECU so no need to change the battery just the module and so on.
One faulty component can trigger fault codes in few other components and if they have limited knowledge about A8s you will end up having all the parts changed but not the one which actually is causing the problem which could be the case here looking at the list of stuff you've had replaced.

This sounds like a fault that I and others have had - crankshaft position sensor needs replacing with a new one - cost about £140 for the part and 4-6 hours labour. The CPS works fine when cold and when hot can make it seem like the starter motor is failing on the car but it is actually stopping the car from starting because it is affected by the heat of the warm engine as it fails / breaks down and so when you wait for it to cool down, all becomes ok again.

Have you scanned the car with VCDS? You will get a code come up which helps to confirm it, but I can't remember what code it was. If you ignore it then it will slowly get worse until one day it totally fails like mine did and the car needs to be trailered to the garage to have the CP sensor swapped

Can only re-iterate that its best to get to someone who can scan it using VCDS which will give you the best chance of finding the issue - rather than taking potshots at potential failure items with the inevitable hit and miss results /costs you seem to have already experienced.
And ALWAYS ask your garage for the old part unless its been traded in/returned as part of the deal for the new part. At least YOU can offset the cost of the new part (when it doesnt solve the problem) by selling the old (still functioning) one online. +++

PM me and if we can arrange a meet I'll do a VCDS scan for you to upload to the forum.
I'm in Wigan which is not a million miles from you, and there are others a bit nearer who might also come up.

Thanks for the offer to scan. I'm very happy to come to you. Let me know when's convenient. Thanks again most appreciated.