2009 vw jetta tdi will not start though engine is turnig enough to start

are you getting fuel and spark? you should be getting air

if you stick the key in the ignition and turn it to the 'on' position, can you hear the pump whirrring before you turn it more to engage the tooth?

open the hood and put your nose into the shnooker, can you smell gas at all?

TDI = diesel engine. No gas smell. No spark. No coil. --- That leaves the glow plugs and the fuel delivery.

glow plugs are only for when the vehicle is starting and they only help as it is compression ignition. you still need to get fuel to the cylinder to get it to run do you have a check engine light

does your car have an immobilizer? been looking at a few forums and it could be water in the fuel, bad fuel, bad ignition switch or an immobilizer.

So it cranks, plenty fast, but doesn't start, have you checked to see if it has an immobilizer, checked the fuel pumps, checked to see if there's water in the fuel, or anything else. Obviously we can rule out your starter and battery.

If I wind it over and over and pump the throttle several time it may eventually start when battery is nearly exausted. But only happens every so often which can leave me stranded.

you are putting it into the on position and waiting until the glow plugs warm up first, before engaging start? this is diesel 101 here~

Ok thank you .

Tell me about glow plugs . How to identify if it is the problem.?

Very grateful for all your help . Will let you know how we go with it ..

they won't glow...that's where a problem may happen...once it cranks over and gets running there won't be any need for them...it's a diesel...the amount of compression creates the ignition~

remember "dieseling" when a car won't shut off? same concept keeps on a goin' and a goin as long as the fuel supply is there~

It is called "detonation" where the mix fires without even asking (from a spark)...with a diesel, that should be ALL you have, if it is normal~

What was the problem here?

If the glow plugs were bad, a fault would have been indicated, and that would have lit the Check Engine light