From the time he purchased the American Diner in 2006 to the moment his Norwood-area restaurant went up in smoke six weeks ago, Mohammed Quadir tried everything to keep his business afloat. He changed the name, focused on cleanliness, tweaked the menu and introduced new specials and discounts. He even hosted play readings and a gothic-style wedding.

He often solicited his customers’ advice, looking for any way to bring back the crowds that once packed the East 204th Street diner, a popular neighborhood gathering spot since it was the Chariot Diner under different owners in the 1990s.

Nothing seemed to work.

This winter, according to city fire marshals and the Bronx District Attorney’s Office, in a final attempt to recoup something from his flailing business venture, Quadir hired a man to set fire to the American Diner — a fire that destroyed not only the restaurant but also the sole neighborhood supermarket and a dentist’s office — and then filed a hefty insurance claim. (The New York Times reported that Quadir had taken out a $500,000 insurance policy before the fire.)

On Jan. 13, city fire marshals arrested Christopher Gooding, 52, in connection with the diner fire. Two days later, fire marshals arrested Quadir, 51, and charged him with paying Gooding to set the blaze.

On Dec. 21, investigators say Quadir left the diner’s front door open for Gooding, who, during the middle of the night, entered the diner and went down into the basement. Gooding then took a quart of gasoline, poured it onto a shelf laden with cardboard boxes and then used a match to ignite the fire, investigators said.

Quadir is now out on bail, while Gooding remains locked up on Riker’s Island. Both have pleaded “not guilty” to arson and other charges. Quadir did not return phone messages seeking comment.

The fire that engulfed the diner, supermarket and dentist’s office came on the heels of another devastating inferno, just down the block on Bainbridge Avenue, which leveled 10 businesses and damaged four others only two months earlier.

The magnitude, proximity and timing of the fires immediately sparked rumors of arson among local residents.

William Law, the northern division commander of the Fire Department’s Bureau of Investigation, said two of his investigators were called to the scene of the diner fire while it was still in progress. Law said his office heard the arson rumors.

Law wouldn’t go into details about the evidence against Quadir and Gooding, but said the arrests were the “result of a lot of hard work, a significant team effort.”

Law said investigators have not found any connection between the Bainbridge Avenue and 204th Street fires. The latter, Law said, is still under investigation. Just last week, Law and his team looked on as a back hoe ripped through some of the rubble on 204th Street, clearing the way for further investigation.

Residents say the American Diner, formerly the Norwood Star Diner, had been struggling to attract customers for the last couple of years.

“For some reason, the neighborhood kind of walked away from it,” said John Andert, who has lived in the area with his partner for several years.

When he considered moving to Norwood, the diner’s presence, with its long hours, steady business and comforting menu, reassured Andert that he would be able to live in the neighborhood.

Ken Small has lived in the area for 20 years. Over the past five or six years, he and his daughter met for dinner at the American Diner, and its previous incarnations, once or twice a month. When they first started dining there, Small said the place was packed on Sunday nights. “Lately, if [Quadir] was lucky, the diner would be half full,” he said.

In 2007, a year after Quadir bought the restaurant, it was shut down for a week after amassing too many health code violations. State Senator Jeff Klein publicly called the restaurant out for being among the dirtiest in the city. Quadir soon remedied the violations and received a clean bill of health from inspectors, but said he lost at least $30,000.

In the months leading up to the diner fire, Andert, his partner and another local, Narani O’Shaughnessy, brainstormed ways to bring people back to the diner. They put on a play reading and talked about doing a Bingo night.

“He’s a really sweet guy who had really high expectations,” Andert said of Quadir. “I don’t know why the business didn’t thrive.”

After the Halloween fire destroyed several indirect competitors – a Dunkin’ Donuts, a bakery, a Latin restaurant – business seemed to pick up, Andert said. But Andert and others said Quadir appeared down about the state of his business and often talked about cutting staff and scaling back hours.

O’Shaughnessy called Quadir a “very gentle man,” but said he seemed “sad and anxious” lately.

“It was shocking,” she said. “It is shocking.”