1.4 hdi 2003 citroen c3 under -15C cold start problem

Car starts perfect always till -15 If it was -20 at night it is very possible that next day it will start after long (about 2 minutes) cranking After starting further it works fine. Person who drove this car previous winter told me that he wanted to solve this problem: fuel injectors and glow plugs were tested and was fine in 2010 spring fuel filter was changed There are no changes now. In winter 2010 the problem occurred again. someone find out that in "very cold weather" some plastic parts of diesel fuel system have micro-cracks or something like that, and air gets into fuel system. Would like to find someone with similar experience and positive solution.