This is a new one for me. My 97 Spyderw/stock 4g64engine was running fine but would not restart after shutdown. It makes that sickening sound they make when the timing belt breaks. I removed the oil cap to see if the rockers were moving when the the engine turned over and they were not. Great! The belt broke while starting. No bent valves. I then pulled the timing cover to find the timing belt tight and intact. I cranked it over again and the engine turns over and thealternator and power steering pump belts are turning with the crankbut the timing belt and camare not moving.Anyone have any idea what has happened?

 

sounds like maybe bearings may have siezed up or a rod is broke somewhere in there.

 

This doesn't make any sense.
Your crank spins but not the cams? You say there's no bent valves...how do you know this? Did you remove them?
If the crank is moving the pulley to move the accessory belts, then your belt is loose or there's something in the head that is keeping the cams from moving. So, is it the cams, lifters, or valves that are locked?

What were you doing with your car, btw? Did you rev your motor too high (float)?

 

I am hoping there are no bent valves. I have not pulled the head yet. I assumed the valves were not bent because the engine was running fine whenit was shut off. After sitting for an hour it would not restart.The crank rotates freely and the bottom end sounds intact. The timing belt is as tight as a new belt installation. Could the key be sheared on the crank sprocket or stripped from the belt?I dont have enough experience with a 4g64 or any other Mitsubishi engine to diagnose what happened. All my experience has been with big blocks and small blocks.

 

Either a guide pin broke between the pulley and the shaft of crank or cam or the belt is missing teeth and just spinning or the cam broke close to the pulley.
You have to set the timing again with a new belt being certain that both intake and exhaust rockers on no1 cylinder is loose as it's in the compression strap me and not the intake strike or 180^ out.
If you have interference engine be preosr d for damaged valves.

 

your timing belt teeth have striped off the belt at the crankshaft remove the belt and you will see