Q: Car doesn't start after head gasket replacement

Hi there. If the engine will not crank then the starter circuit needs to be tested to see if there is a wiring issue. If it is cranking and not starting then the computer needs to be checked with a scan tool to see if it is getting a crank signal from the crank sensor. If not then it may be a sensor or circuit problem. If all of the sensors check out the security system may be causing this. If the security light is on when you try to crank the engine then it is the issue. This can be a programming issue or a problem with the passlock sensor. A computer scan tool would be needed to test those. If you need to have this looked at, consider YourMechanic, as a certified mechanic can come to your home or office to inspect your vehicle.