My silverado cranks but will not start sometimes. If I wait about 10 minutes it usually starts up. My security light stays on. need help...

Do you mean it cranks but will not fire?

yes. it does crank.

When this happens see if you have spark and check the fuel pressure at the rail. If it was in the factory security system it usually would not crank.

i have just read an article about silvie no starts related to security issues.
1. scope your codes. there's a specific error code that is related to security issues.
2. if you have it, then do this: insert the key, turn appliences to on, so that security light comes up, and let it flash. let it flash untill it goes solid. try to start the engine. if starts but stalls right away, light should start flashing again. let it flash until it goes away. they say it may take up to 30 minutes.
'ts called Relearning procedure, has something to do with body control module and security system.
good luck.