My fuel pump quit on the last field this year.  It wouldn't pull, but I geared down and finished.  Next morning, no starty.  It's just a big electric fuel pump...i bought one from a go-fast place for half what Deere wanted. 

Curious what was so difficult about the hydraulic pump....really no different then any other Deere of the vintage.  Anyone who has rebuilt one on a 4020 ought to be able to handle the project.