Tribune photo illustrationTribune photo illustrationWalid Mendez grabbed a Blue Line train for work Wednesday morning and was settling in near the door when he felt a breeze at his back. Passengers around him started yelling.Mendez turned to see the door still open as the train, about 40 feet off the ground, pulled out of the Damen station and started picking up speed toward the Division stop.People rushed from the door. Mendez, 28, said he grabbed a pole and helped an older woman. “She didn’t have any place to grab onto,” he said. “I grabbed on her shoulder with my right arm.“Everyone was yelling for someone to pull the emergency brake,” he added.At first, passengers pulled the red knob near the open door but nothing happened, Mendez said.As the train moved faster, a man near the door between cars pulled an emergency brake knob hanging near him and the train quickly came to a stop, Mendez said. A CTA worker came through the train and pressed something in the well of the emergency knob to reset the doors, closing them, and the train was able to move on, Mendez said. The worker stayed in the car for the rest of the trip as the train traveled express from Chicago Avenue to Clark and LaSalle, where Mendez got off the train.After he got to work, one of Mendez’s coworkers who waited on the Damen platform for the next train told him that other doors on that train were also having trouble closing.The CTA sent out a tweet at 8:48 a.m., about 10 minutes after the door malfunctioned, saying that Forest Park-bound Blue Line trains were operating with delays “after … earlier door problems at Damen.” A CTA spokesman said the train operator informed the CTA control center about a problem on his 2600 Series train and passengers were taken off the train and transferred to another.The 2600 Series trains are the oldest trains still operating in the CTA fleet, built by Budd Company/Transit America from 1981-1987. They are known for their door problems and many of the cars have been scrapped.As designed, if the doors do not close when the operator activates the close-door switch, a failsafe system is supposed to prevent the train from moving. Or, if it does start to move, to stop the train, according to CTA officials. A customer pulling on the red bulb above the door would send a signal that is supposed to automatically stop the train, officials said.Mendez said he was jarred awake by the experience. “Who needs coffee when you have something like that in the morning?”Mendez said he has ignored the regular warning to passengers not to lean on the doors, figuring the train couldn’t go anywhere if the doors were closed.“I’m going to listen to that warning,” Mendez said.