That is all part of the spin on fuel filter changing process. Crack the bolt, I think it's 21mm? at the top of the fuel filter. Then use the manual fuel pump and pump it until all the bubbles are out of the line and fuel leaks out the top of the bleed bolt as aforementioned. Crank the car with the pedal down on a
fully charged battery and off you go.
I must say, the 300D W115 is the hardest diesel I have ever had to prime. It's quite frustrating actually.
