Given that there was a major delay was at the start, not the bridge, with more later (east of Sacramento) with the report of a helper engine, the "engine trouble" diagnosis seems likely. Circumstantially, #6's issues may have also affected the San Joaquins (711 terminating at Emeryville instead of Oakland/714 starting at Emeryville an hour late) in the area at the time. The delays began in the Oakland area, not at the bridge.