The incident happened on Friday afternoon in the car park at Garrison Place in Falkirk, which is just behind the Morrisons petrol forecourt.
Bryan and Stacey Moffat, who own the Picturesque, by Mr and Mrs M photography studio, captured the fire on video.
Bryan said: “We had just nipped out for a coffee when we saw the flames and smoke.
“It was quite scary because it was close to the petrol station.”
The Scottish Fire and Rescue Service said it received a call at 12.36pm and firefighters used two high pressure hoses to extinguish the blaze quickly. The incident was under control by 1.10pm.
A Police Scotland spokesperson said the fire was caused by an electrical fault in the engine.