Your 3.0 liter V6 is not an interference engine so it should just stop running
If it breaks while the engine is runnIng, yes. It can damage the valve train
Yes , the 1.5 liter engine in a 1991 Toyota Tercel IS AN INTERFERENCE ENGINE so if the timing belt breaks while the engine is running it can cause engine damage
Your car breaks down and you cant move at all until you find a garage then it costs a fortune! Running petrol in a diesel engine will destroy that diesel engine.
when it breaks
It will quit running if it breaks. That's the most common failure of a timing belt. It may run poorly and backfire if it slips or jumps a cog.
Serious internal engine damage will occur. Replace the belt every 90,000 miles.
before it breaks
It depends on what is broken - please be more specific...
YES, And depending on the type of engine it can total the engine if it breaks.
If the timing belt breaks, the valves get bent immediately.
Before it breaks
Engine will stop running. Also on the 3.0 Liter V6 there will be no internal damage, but on the 3.4 L V6 and the 4.7 L V8 there will be engine damage as these 2 engines are interference engines.