Mercedes Benz repair: 96 e300 diesel, air bubbles, fuel filter

Question
a few weeks ago..whenever cold starting.the engine would fire right up...then imediatly die...After some cranking it would usually start the secnd time....starting yesterday.the same thing would happen at start up..but now it takes minutes of cranking (and a jump start to get it going) once the engine is warmed up it starts right up every time....in 2 of the 4 clear fuel hoses running to the fuel filter you can definetly see air bubbles...but nothing seems to be leaking on the ground.....HELP !!!..thank you mark

Answer
Sucking air:
There are rubber O rings on the (roughly 19mm) plastic insert attached to the top of the fuel filter housing, between fuel filter mount bolt and head, return fuel flows through the tube, transitions through the insert, and is returned to the fuel filter.
You remove the tube, remove the retainer, and remove the transition insert to replace O rings.
I can not recall if there are three or four O rings, replace all other O rings on fuel filter housing lines.
Inspect all tubes for micro cracking, brittleness and discoloration, replace them if in doubt.
Replace fuel filter at the same time, fill it with diesel before you install.