Poor starting and white smoke

[Ianb4310]

Hi everyone I've read lots of posts on this all seem to have same problem when left for a long period of time 4hrs etc car struggles to start it turns over fine but it like its not catching I let glow plug light go out then turn if I put glow plugs on a couple of times it's a little better not much but it always starts second turn ?
After reading other posts seems it could be
1 thermostat
2 temp sensor
3 maf
4 glow plugs
5 pump timing

I'm going to replace temp sensor first as its cheapest and easiest could someone please post a picture of exact location
Car is a 2002 A6 2.5 tdi
Thanks
Ian

 

[marsmail]

Hi,
I had a similar sounding problem with a van some years ago. It was diagnosed as the box which told the glow plugs if they were needed having failed. Had to churn it over until (presumably) the compression raised the temp enough to start it firing, lots of white smoke while that happened.
Electronic box changed, problem solved.
Hope this helps

marsmail

 

[kenton]

HI this may be of use.
poor starting can also be due to air getting in to the fuel this can also give a misfire under load but is easy to check take a look at the clear pipes going to the pump from the filter if there is lots of air bubbles you have found the fault. hope this helps.

kenton

 

[ms1083]

i have 2004 a6 2.5tdi v6 allroad.

when i checked them all 6 glow plugs were not working, after changing them much better starting. 1 of them was a sod to replace, the others were v easy, suggest you pick 1 of the easy to remove ones and connect to battery to test. if not working replace them all.

coolant temp sensor v easy & cheap to replace. its under the engine cover, near the front, has a green plastic clip holding it in place. 10 min job. i partly drained coolant before doing to stop any leakage, not sure if you need to do that or not, i only did it from the coolant tank by suction.

just a little comment, these engines are known for the diesel injection pump failing, first sign of this is poor starting!

i have bought a vag fault code reader from ebay - well worth getting, any timing issues will throw engine fault codes.