My son is off at college 7 hours away. He called today to let me know his 2003 Elantra won't start. It cranks, tries to strart, but doesn't. My son isn't mechanical so tough to determine exactly what is happening over the phone. We just replaced did a bunch of work on the vehicle: replaced the timing belt, tuned the engine replacing plugs and wires, replaced the waterpump and alternator. Any ideas on what could be keeping it from starting?