I have an 02 trailblazer.When i start it in the morning or when its been sitting for a while, it starts and runs perfectly fine. but if i go on a small like 5-10 min trip then turn it off, when i go to start it again, it will crank and crank and crank but will not start. i have to keep trying it a couple times and then it will eventully start and then usually the rpms will be real high when it does start then goes down. i replaced the ignition switch and spark plugs but it did not fix it. does anyone have an answer to what it might be THANKS...

anyone?

Extended cranking can be caused by many things, restricted fuel filter, poor quality gas, weak spark, low fuel pressure, inoperative or carboned up iac, or throttle body, no set one answer issue here. Leaking fuel injector, leaking fuel pressure regulator also.