John Richardson Sr., a well-known mechanic at 3 G’s Tire in Portland who served customers in the Portland area for 37 years, died Sunday after a battle with cancer. He was 48.

Mr. Richardson grew up on Oxford Street in Portland and attended the former Jack Elementary School and King Middle School. He decided not to attend Portland High School. Instead, he went to work at the garage, then known as Dyers Tires.

Mr. Richardson began working at Dyers when he was 11 years old. As a boy, he did odd jobs like cleaning and unloading trucks. He eventually learned how to fix and change tires, and in the ensuing years he became a full-fledged auto mechanic.

Mr. Richardson was remembered Tuesday as a knowledgeable and trustworthy mechanic who went above and beyond to help customers.

“It wasn’t unusual for him and I to open the garage at 8:30 p.m. to help a customer with a flat tire,” said Dennis Hewitt, the owner of 3 G’s Tire. “He was very good at his job. John wasn’t the type to get certifications and things like that. He was more of a hands-on guy. Once he learned something, he got it down.”

Mr. Richardson was a fixture at the garage for 37 years. Hewitt said many customers requested Richardson to work on their cars.

“An automobile is so important in today’s world. People trusted him,” he said.

Mr. Richardson was diagnosed with cancer about a year and a half ago. Doctors suggested that he file for disability, but he wanted to keep working. He returned to 3 G’s to work at the front desk as a service writer. His last day was Dec. 24.

“He will be missed by a lot of people,” Hewitt said.

In his early years, Mr. Richardson was a fixture at Beech Ridge Motor Speedway in Scarborough. He had a passion for cars, both fixing and racing them. He won many races, including a championship title in 1999.

Richardson’s younger sister, Regina Fernald of Buxton, said he was known on the track as Dirty 30. She said he would use his car to tap other driver’s cars to get out of his way. He raced for about 15 years.

“He loved working with his hands and the thrill of the win,” his sister said. “He would get sick as a dog before the race, then he would go give it his all. … Everyone out there loved him. He definitely left a mark.”

Mr. Richardson, of Standish, was previously married and had two children. Fernald said he loved his children and was close to his grandchildren. She said he liked getting down on the floor to play with the younger kids.

“His grandchildren were his world,” his sister said. “It was a bond. He looked forward to seeing them.”