Does not start Passat 1.9 TDI 115 hp of 99

Hello, I have a Passat 1.9 TDI 115 hp of 99 (AJM engine), a few weeks ago it began to have difficulty starting cold, they were sometimes but lastly to penalties it was parked 20 minutes until it stopped starting. In the workshop I have looked at the aforerator (this model does not carry a bomb, only a loafer) and the mechanic does not know if it is because of the tandem I understand that the bomb cannot be because my car did not lose diesel or anything, but I am not an expert
good I hope someone can give me a useful opinion
thanks