The 47 year old Spaniard made a perfect start, and with Rumford paring the first two Jiménez was immediately on his shoulder at Blackstone GC in Icheon.
Dane Søren Kjeldsen, who shared second place with Jiménez overnight on seven under, also reduced the deficit with a birdie of his own at the par four second to move into sole possession of third place.
Scot Richie Ramsay, American Ryder Cup star Dustin Johnson and Welshman Rhys Davies had all advanced to seven under for the week in the early stages of Moving Day.
South African Jbe Kruger had made the most progress - playing his first ten holes in five under par he was up into a share for seventh.
Sitting ominously alongside him was World Number One Lee Westwood, who like Jiménez birdied his first two holes.