Port Vale, having already lost to Crewe twice this season, might of had a psychological disadvantage today but with it being the FA Cup the form book counts for nothing.
Both sides started well and Crewe troubled the goal in the 11th minute when Rodney Jack pulled the ball back from the right, and Kenny Lunt struck a weak shot which was easily saved by Mark Goodlad.
Vale went close in the 15th when centre back Sam Collins came forward to cross from the right which found Michael Cummins who headed barely wide of Clayton Ince's left post.
Poor defending by Vale four minutes later led to a Crewe corner, which Ben Rix duly crossed to find the boot of Rob Hulse, but his bullet shot hit off the bar and was cleared.
Crewe could of scored a vital goal right before the half-time whistle when Lunt played a through ball to Jack who took it to the right of the box and struck a drive that brought the best out of Goodlad to palm it wide.
With honours even at the break, both teams would have to keep up the pressure to break the deadlock.
A ball down the left by Jack for Rix allowed him to get round his marker and release a shot from 16 yards that had Goodlad at full stretch high to his right in the 69th minute.
A quick break in the 80th minute by Vale was stopped sharply by the Crewe defence, but Cummins found himself in space 20 yards out and hit a strong drive that narrowly flew over the bar.
Crewe finally cracked it when a mazy run down the left by Jack in the 85th minute gave him space to spread the ball to the right side where Dean Ashton steadied himself and fired a crisp shot cleanly into the bottom right corner.
Alex boss Dario Gradi was modest about the result: "Dean did just enough to win the game and managed his finish well, to win three times at Port Vale is no mean feat, its brilliant."