Checking rail pressure while cranking

[Rawze]

(11-12-2019 )Konstantin Wrote:  ...
it also changes sound at the same time when it looses 10 psi pressure and goes to 0.
...

Mine does this when it is sucking air after a davco change.

Maybe air getting into the fuel somewhere?

{edit}
--- AHHH,.. I see you solved it. Thanks for sharing.