On a recent afternoon, Jacob Long gave a tour of the Connecticut wool mill that has become his biggest investment, his life’s mission and an unrelenting source of worry.

A factory building murkily lit even in daylight, the vast space contains 40 high-speed looms, as well as decommissioned spinning equipment that was thrown in when he bought the mill 11 years ago even though he had no experience in textile manufacturing.

Mr. Long, 54, talks quickly and bounds rather than walks. More than one colleague described him as the Energizer Bunny. He wears slim-fitting dress shirts, slim-cut trousers and chunky, stylish eyeglasses. Having worked as a banker in Europe for 25 years, he now comes off as a stranger in his own country: He speaks fluent Italian and sometimes struggles to come up with the American word or phrase to describe something.

He led the way past the old, idle equipment to a prized new machine, a German-made sample warper that cost $300,000. It was an essential part of his grand plan to revive America’s craft textile heritage — and finally make a profit.

“I convinced my wife to sell her last apartment in Italy to buy this machine,” Mr. Long said, adding with a nervous laugh: “Please don’t talk to my wife.”

For a decade, Mr. Long has been delivering a well-worn — and largely ignored — sales pitch for his improbable venture, comparing it to the craft breweries that uplifted local economies with an emphasis on quality over quantity.