Problem Starting 3.0 TDI Auto

[Mark_A4]

Can anyone help with some advice on the following issue...

Audi A4 2006 TDi 3.0 Avant Auto.... I am having problems starting the car - it's been in to various independent garages and had two visits to Audi with no success and a hefty dent to my wallet. When I attempt to start the car, I turn on the ignition to glow plug position then pause until the glow light goes out then turn past to engage the starter and nothing happens - no sound and no turning over of the engine. Then if I take the key out and put it back in and immediately turn the key all the way round (past the glow plug position) to engage the starter, the engine will turn over for about 1 second and fail to start. After doing this about 80 times, the car will start. Other symptoms: The light on the auto box gear selector for the foot brake doesn't light up. After the 80 or so turns, the light on the foot brake lights up and the car starts up fine. If I then turn off the car, and try restarting as normal, it  starts fine and will continue to start properly until such time as the car is turned off for about 6 hours or longer. After this period of time I have the same starting issues again. The first time it went to Audi they said it was contaminated fuel and charged a small fortune to clean everything out. It didn't fix the problem as when they had it, they didn't have the 6 hour delay from being started. It went back to Audi again and they diagnosed it and found nothing. They allegedly checked the gearbox is ok and the wiring is ok and they said they couldn't find anything. The issue appears to be a time related problem. If I have stopped the car, provided I start it without having left it for more than 6 hours, it will start fine. If it is left longer than 6 hours, it won't start unless I go through the procedure of inserting the key and turning it straight to crank the engine over for a second about 80 or more times.

It would appear to me to be like the constant turning of the key is charging something up so that once it has enough charge the car will start. Likewise, once the car has been running, the charge is present so the car will start up. After 6 hours or so, the charge has drained away and the process need to be repeated to recharge something.

Can someone help as this is driving me mad so much so that I am thinking about getting rid of an otherwise great car?

[Trevor]

Hi Mark...welcome to the Forum

Wow!  that's a humdinger of a fault.

I think the first place I would go to is the engine oil and condition of the cylinders. Sounds silly but it would be the cheapest place to start before spending any more money on the car. If you look at the condition of the oil...is it washed-down with diesel fuel (i would be surprised if it wasn't after all the cranking over). If is stinks of fuel, then drain it and refill with correct grade. This can affect the cylinder compressions which will need to be at a high level to aid combustion so if diluted it will not achieve this.

Also check the fuel filter and replace with another (quality and OE if possible) if in doubt. Again another cheap option to start with. If the filter or the filter head is drawing air, it will not draw fuel and then the system won't become active until it gets the required fuel pressure in the fuel rail/pump. Had this problem on a Nissan and changed the filter head...cured it!

Let us know how you get on with it 

Cheers  Trevor