The timing marks on my 2.5TDi (ACV engine) are very subtle and take the form of a '0' with a line through it. It can be difficult to find looking through the bell housing aperture. Don't forget that the pump only lines up every second crank revolution.
If you get an assistant to turn the crank, look carefully for the timing marks with a bright light with your head down near the aperture.
Kevin
March 2008