As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER ENGINE START HAD SMOKE IN THE COCKPIT AND CABIN THROUGH THE ENVIROMENTAL SYSTEM. FOUND THE LEFT PRESSURIZATION PACK SHUTOFF VALVE STUCK OPEN CAUSING PAC OVERHEAT AND SMOKE IN THE CABIN. REPLACED THE PRESSURE REGULATOR SHUTOFF VALVE. SYSTEM CHECKED GOOD THE AIRCRAFT WAS RELEASED TO SERVICE. (M)