Thread: Setting TDC - necessary?

Not necessary, i have replaced/ repaired both and didnt set TDC either time.
Its a fiddly job getting to the bolts thats made harder when you have to account for the tension on the drive arm against the cam lobe but not impossible.

FInding roughly TDC is only really useful when reinstalling - then the lobe which operates each unit will be on its low side - that way the new pump won't be pushing against it when doing up the bolts. When you take the first one off, either the lift pump or vacuum unit, you may notice that the unit may be pushed outwards toward the nuts when undoing. Undo all the fasteners evenly so the pump does not get pushed to one side. Once its off, you will see the operating cam through the hole - if you need to, just rotate the crank until its on the low point, then you are good to reinstall and start on the other one.