Car cranks will not start

She had a mechanic replace the head gasket and water pump and timing belt. When he got done the car would not start. Just cranks. So I told her I would look at it. I figured he was off on his timing marks. Well the marks did not line up. He had the sprocket on the number one Cam upside down. So I fixed that and all the marks lined up perfect. But it still did not start. And when I turn the key to start it and then let off the key it still turns over for a few seconds. Any ideas what it is?