He likely had water and/ or trash in the "new" fuel in the antique gas can that has been sitting in the shed open most of its life. It happens more than people will admit.
No one ever looks in a gas can before filling it to see all the water and trash that has collected over time. they just keep refilling the stupid things and wonder why they have problems.
I have caught that problem several times in my gas cans only to stop and drive back to the shop & flush them out good before going back later to get fuel.