[Jainer]

Hello, my 2008 V6 TDI BKS have been problems recently with cold starts. It takes about 8-10 seconds since ingnitions engage for the engine to start, and when it finaly does there is a huge white smoke cloud.

VCDS show me that ther was a short circuit with 2 glow plugs , so I thought that maight be the problem. So I replaced all six glow plugs with new ones (Bosch Duraterm 0 250 403 009) and installed a brand new battery. Now VCDS dosent show any fault codes and everything seems to be ok, but the start problems continue and nothing improved.

My hypothesis is that the time that the glow plugs stay lit is not enough; since if I do three or four ignitions before start, the car starts without problems.

Is there a way to improve the time that the glow plugs stay on?

 

[RocketTech]

Have you checked your oil level lately? Sounds like leaky injector(s).

 

[Jainer]

Have you checked your oil level lately? Sounds like leaky injector(s).

No I haven´t but I was planning to do it because I have a ticking sound coming from one of the injectors. The oil level it's fine, the engine is not burning oil at all.

But, how could a leaky injector affect the time it takes for the car to do cold start?

 

[RocketTech]

A 12 yo Diesel that doesn't consume any oil? That's pretty strong evidence of a leaky injector right there.

A leaky injector probably won't develop a proper spray pattern, and will probably also burn too rich. The white clouds of smoke are a sign of un-burned fuel at low temperatures. Too much fuel, or fuel in drops rather than mist is harder to ignite.
It could be something else, but it's looking like a leaky injector.

 

[Jainer]

A 12 yo Diesel that doesn't consume any oil? That's pretty strong evidence of a leaky injector right there.

A leaky injector probably won't develop a proper spray pattern, and will probably also burn too rich. The white clouds of smoke are a sign of un-burned fuel at low temperatures. Too much fuel, or fuel in drops rather than mist is harder to ignite.
It could be something else, but it's looking like a leaky injector.

Hi Rocket, thanks for the advise

I alrready check the inyector, It was just a faulty inyector, no oils leak present on the cylinder chamber.

The white smok its only present on the first start when the car its cold, no smok present while the motor is running or during acelerations; not even in the engine start throughout the day.

I believe the smoke is due to excess diesel in the cylinders, because the pump continues injecting on every rev until the necessary temperature is reached in the cylinder chamber for the diesel to explode.

Perhaps if you could increase the time the glow plugs stay on before the start, the temperature in the cylinder chamber would be reached faster and therefore the cold start would be successful and would not allow the cylinder to be flooded with diesel...but I can't figure out how to increase this time.

 

[RocketTech]

Jainer- no worries
Oil wouldn't necessarily be leaking into the cylinder- that would be from piston rings or valve seals- the issue would be Diesel leaking out of your injector, puddling on/around your piston, and leaking down past the rings into your oil.
White smoke on startup is somewhat normal, especially during colder temperatures. It's much less common during summer months and more indicative of a leaky injector.
Yup, you're exactly right about it being from excess Diesel in the combustion chamber, but these are CRD engines which varies the injected amount to suit conditions- it shouldn't be injecting excess Diesel. The HPFP pressurizes the fuel, the engine computer controls timing and injection volume (stroke)- very similar to gasoline EFI. Basically there is much greater control over injection events. The other thing is Diesel must ignite upon injection- it won't ignite, or won't ignite properly if it doesn't burn upon injection. When Diesel doesn't ignite as it's injected, you can get issues similar to knocking/overheating/burnt pistons/burnt heads/slagged exhaust manifolds. Unburned Diesel will drain into your oil. You wouldn't want Diesel burning at a different time, and the odds of it doing so are slim.
Glow plugs heat the air in the cylinder- not necessarily the cylinder itself. Glow plugs typically do run after starting for a short time, but this is controlled by the engine computer. Your cylinder flooding with diesel is a problem with the injection system or engine management, not glow plugs. Increasing the glow plug active time could cause alot of problems, most of them expensive to remedy.
Hope this helps!