Four months later, an obscure Texas startup called America First Refining announced that it had received a nine-figure investment from the Ambanis’ company. The deal puzzled numerous energy investors familiar with the project, which aims to build the first major new oil refinery in the U.S. in about 50 years. The company is run by a serial entrepreneur with a history of bankruptcy and lawsuits alleging fraud. After more than a decade of failed attempts to raise money, blown deadlines and rebrands, it had been floundering.