Abrupt stop on pull cord

Attempted to get my mower ready last weekend, but can't get the thing to crank. I've changed the oil, fuel filter, air filter, spark plugs, and put new gas in, but it just won't crank. It spins and spins, but won't start up. Not really sure what to look at next so please offer me some suggestions.

Yes me dad has a John Deere STX38 and it won't start, he told me last time he mowed it ran fine. When he went to start mower after it sat for about a week the engine will turn over but not fire. He has not tried nothing so I don't know if it has spark or not. I am going to his house to look at it later this week and would like to know where to start. 1. Check it for spark, if it has spark ok if not what should I check? 2. Check for gas getting to carb. and maybe spray some starting fulid in carb. I would say if it starts and runs till fulid burns out it maybe the carb or gas not getting to carb. Thanks for any help with this. Steve