Another thing to check when you xfire won't start is the gear shift linkage/rod. It's the rod that connects your transmission to the shift handle. The rod is secured to the bottom of the shifter handle under the car with an hex(allen) screw. Sometimes, especially if the car was hit in an accident, the rod would slip resulting in your gear not being in park or neutral when you think (or the instrument cluster indicates) it is. Obviously you can't start your car when tranny is in gear.