Garcia holds a one-shot lead after playing just four holes of the final round, sitting at 15-under par for the tournament, one clear of South African Tim Clark (five holes) and Americans Jason Dufner (five holes) and Bud Cauley (four holes) who are 14-under.
Sedgefield Country Club was hit with 1.6 inches of rain overnight and light rain continued on Sunday, but play was able to get underway on time.
However, heavy rain hit the area in the late afternoon forcing 38 players off the course, with 0.6 inches falling before officials decided on a Monday finish.
Chad Campbell (nine holes), reigning FedEx Cup champion Bill Hass (nine holes), Jimmy Walker (eight holes) and Harris English (six holes) are tied fifth at 12-under par.
American Ryder Cup captain Davis Love III sits four shots off the pace having played seven holes, tied with seven others in ninth while defending champion Webb Simpson completed 10 holes and was five back at 10 under par.
Garcia, needing a strong result to force his way into the European Ryder Cup team, started the final round with a one-shot lead but was quickly joined at the top by Clark after the South African claimed a birdie on the second hole.
But the 32-year-old Spaniard knocked his tee shot on the par-three third to five feet and converted the birdie putt to regain the advantage before the suspension of play.
Garcia is searching for an eighth US Tour win, but his first since the 2008 Players Championship, to go with his 10 European Tour victories, two of which came last year.
The delay means several players are still unaware of their FedEx Cup playoff fate, needing to wait for completion of play to see if they have claimed one of the 125 places in the field for The Barclays tournament in New York, which starts on Thursday.