Cold starting problem - 1.8TDCI 03 reg

[bramble]

For the third winter in a row my 03 focus 1.8TDCi is playing up and is difficult to start. Time taken to start is directly related to the outside temperature and even with the recent very cold spell, it always eventually starts. However, the lower the temperature, the longer I have to churn the key and eventually it bursts into life, one or two cylinders a a time. Once we get to April/May it will be fine again till late autumn again!

I am convinced the engine thinks it is warm and therefore doesn't do what it should do when it is actually cold. I have changed the glow plugs - no affect. The glow plug warning light stays on for the same length of time summer or winter (a few seconds only) (although I have put a bulb on glow plug field and they do stay on a bit longer than the light suggests but not much). Again,symptom suggests engine thinks it is warm.

Tried changing the cylinder head temperature sensor (not easy to get to!) and still no difference!

Anyone any ideas? I am sure this is a minor issue (otherwise I am convinced it would have got worse by now) but no idea what! ECU programming perhaps not detecting the engine is cold?

Once it is going it runs like a dream, very good mpg, plenty power, smooth, no smoke (only big puff when it eventually starts when it is cold)

Thanks!

[SierraYankee99]

Glowplugs matey, without a doubt. Even one down will make it a pig to start.