Cranking it with the ignition wire off is a waste of time. On a tight healthy engine the oil pressure comes up within like a second after a change. Even on my 250k+ mile 603 it comes up right away.
I remember when I started my friends S320 right after we did the oil change the guage came up as it was cranking and was at 3 bar right after it caught.
It was probably your tensioner acting up.
