Does “full coverage” help when the engine fails without a crash?

My car stopped running while I was driving, but there wasn’t a collision, weather event, vandalism, or other outside damage. The initial diagnosis points to an internal mechanical failure, and I’m trying to figure out which part of an auto policy, if any, would respond.

The policy has roadside assistance, but I’m unsure whether that only covers towing and similar services or whether it could contribute to the repair. I’m also checking whether it includes mechanical-breakdown coverage. The declarations page lists collision and comprehensive, although I know “full coverage” isn’t a technical promise that every repair is covered.

For this kind of claim, would collision or comprehensive normally apply when the vehicle simply stops running? Or would the repair generally be excluded as wear, maintenance, or mechanical failure unless there’s a separate mechanical-breakdown provision?

The vehicle’s age, mileage, and the repair estimate probably matter too. When contacting the insurer, should I describe the symptom and lack of a crash first, then ask them to review the roadside, mechanical-breakdown, collision, and comprehensive provisions?