2.2 TiD Cold start problems

Good evening to the gentlemen, I needed your advice. Our 2.2TiD recently starts very badly in cold condition, only starts after about five to seven seconds organs. The diesel filter, the leak oil pipes and the plastic distributor pieces, the traverse seals, all vacuum hoses have already been exchanged. I have visited the workshop again today, which has now found out that there is no glow at all. There should be a starting glow and an afterglow apart from the annealing, the Workshop has not been able to diagnose any of these. Of course, there is no stored error code, glow plugs pick up current when you connect it externally. Also the feedback signal of the incandescent control unit arrives at the PSG16, can be read out with the Tech2. Did any of you have a similar problem with the incandescent system? Thank you