07 Impala will not start when engine is warm
 

Please help me. i have been trying to fix this for weeks! Car doesnt start when engine has warmed up. It isnt overheating. Checked battery, starter and alternator. All are fine. i have replaced the starter relay switch and the coolant temp switch. It still does the same thing. After i have used the car around town. And the engine gets to normal running temp. It doest start. Key turns lights turn on but no spark or click. I have to wait about an hour then it turns over again.
Please help
Dan:(