Before attempting to start a car that has been inactive for so long, it is a good idea to drain the old gas and replace it with some fresh fuel. Remove the plugs, squirt oil into the cylinders, while the plugs are out turn the engine over enough to get the oil circulated to prelube the engine. Preform a compression check to see what condition the engine is in. If the compression checks OK. Remove the injectors to see if they squrit fuel. While the injectors are removed, replace the injector seals. Most likely the old Volvo will have an ignation problem of some sort, that will have to be fixed. If you get it started let it idle with the heater on till warmed up, check temp. Make sure it will not overheat. If it has a lack of power, most likely the cam is worn.