On his blog "Getting There" he reports:
Dresser quoted an MTA spokeswoman who said the exact cause of the breakdown was yet to be determined, which may account for the fact that emails notifying passengers of this morning's delays lacked any explanations.
"The breakdown came in one of the AEM-7 electric locomotives that has only recently been returned to the tracks after several years in Amtrak's Wilmington shop. Late last year, Amtrak found the supposed fix, and began reurning the supposedly operative engines to MARC."
The faulty locomotive is back in Amtrak's Washington yard, according to Dresser. For the sake of us commuters whose bosses disapprove of their employees regularly trickling into work 30 minutes late, Dresser warns: "MARC riders had better hope the problem is not related to the AEM-7's previous electrical woes. Otherwise it might be a long winter and spring on the Penn Line."