If a car catches on fire by my car..isn't that guys insurance reesponsible for paying?

He mentioned that the car was smoking. He jus parked it and went to work a few moments later we have a fire. Allstate his insurance is trying to say he isnt at fault b/c the car caught onfire. He admitted to smokin in the car to. If the fire report says that it was mechanical or started from the cigarrette then isnt he liable? I thought u were responsible for the maintenance of your car. If my car is smoking I'm going to get it checked! Would I be right to get a lawyer if his insurance refuses to pay for my car? Can I do that and legally is he responsible for the damage to my car.