Shortly after a fuel leak on a semi-trailer truck was repaired at a dealership, the driver noticed it was leaking again. While en route to the dealership to get it fixed, the driver was unaware that fuel was leaking on the exhaust manifold. The driver was overcome as the A/C system pumped carbon monoxide from the burning fuel into the cabin and struck a parked car in the dealership parking lot. The driver did not realize the degree of incapacitation until the attempt to exit the truck and the individual recognized at what degree the motor functions were diminished.