Company officials said during a conference call with analysts Friday that crews had begun feeding crude oil through the unit knocked out by the Aug. 6 fire.
Chevron's chief financial officer, Patricia Yarrington, says the unit at Richmond is expected to be fully operational during the second quarter.
Both Chevron and government investigations have determined that corrosion in a pipe caused a leak that sparked the fire, sending a plume of black smoke over nearby areas.
Since the fire, the refinery had been operating at about 60 percent capacity until very recently. The factory wasn't processing crude oil and instead was being used to blend gasoline.