Chilton's manual #48300 1974-84 MBs states on 1-42 "To bleed the injection pump on 5 cylinder engines, open the bleed screw on top of the filter housing .... then operate the manual pump until the fuel emerges free of bubbles."
Unless I mistake Diesel Giant and others, this is bunk and will introduce air into the system ... just pump without cracking the lines.
So which do you believe?
I lean toward the politically correct No Crack method.