acts like it wants to crank but dont geting fire

thanks i was thinking fuel pump but wishing it wasnt got fire from plugs.how do i check the anti theft system

When you turn the key to the on position, but not to the crank (start) position, does the "THEFT" light flash or stay solid? Flashing means a problem with the PATS function Solid means the key is checking out ok.

its been flashing

Bingo. The light flashing means that your key and your truck are not communicating. Are you using a spare key or a new key? If so, try an old one. If not, you may have a transceiver problem or other issues. Have a diagnosis performed...nothing else you can do by yourself on this one, I'm afraid. Other than trying the other key...