What could be the problem

https://www.google.com/search?q=Nissan+NP200+1.5+DCI+loses+power

and

https://www.google.com/search?q=Nissan+NP200+1.5+DCI+glow+plug+light+comes+on

..

Sounds like the timer is bad. Since you have power when warm, the power relay must be giving the timer juice. The way it is suppose to work is you wait until the glow plug light goes out and then try to start. In cold weather it should take longer for the glow plug light to go out.

What color smoke? White=head gasket. Black=... Post the color of the smoke, and whether or not you have heat.

p100d error code is due to fault in EGR Valve.The EGR valve shuts off to when 3000rpm is exceeded.so the EGR Valve needs to be checked and replaced. Thanks. you can rate this solution and show your appreciation.

sounds like a glow plug problem,if it starts o.k. when warm,but not when cold,does it smoke a lot when trying to start it cold,if so i would say your glow plugs are either burned out or theres no power to them when you turn on the key,do you see the glow plug light on the dash,it may light,but that doesn,t mean the glow plugs are getting power

looks like either glow plugs have gone or possibly the pre-heater sytem is faulty.
the car should start even though the glow plugs are slow to pre heat unless its a further gremlin

I would suggest you check oil levels etc. Generally these cars suffer from the air mass meter / air sensor problems aswell as coil problems too. Did you ever get a solution to the problem?

on some diesel engines the glow plugs will cycle after the engine is started. it does sound like your glow plugs are not all working that would cause the hard start and excessive smoke when it does start.

when were your glow plugs last changed, if not within last 1yr i would change them, otherwise it may be your relay both are inexpensive so worth trying first

hi from uk just a couple of questions ? as car is now with this cold starting?? when engine does start do you get blue/black heavy smoke and engine has a slight hesitant ? then smoke clears ? engine runs ok? and no problems starting for rest of day ? if this sounds like the problem you have? then this is the glow plugs that arenot working at optimum you only need 1 or 2 poor and engine has trouble cold starting may i suggest you first check that when you put ign on there is power reaching the 1st glow plug at least? if ok this will eliminate relay and fused link? these glow plugs must glow white hot from tip upwards you can change these diy with a little patience and are obtainable fro most motor super shops here in uk anyway hope this helps?and inspires you? please update on how you go on? or if you req further info ?