What was found
(CAN) DURING TAKEOFF ROLL, ACFT VEERED TO THE RT. CREWS PULLED POWER BACK AND RETURNED TO BLOCKS. FOUND THE LEFT ENGINE BLEED FIREWALL SHUTOFF VALVE WAS STUCK IN THE CLOSED POSITION AND THE CREW DID NOT NOTICE THE FAULT DURING START CHECKLIST. THE VALVE BEING IN THE CLOSED POSITION MADE THE RUDDER BOOST SYSTEM THINK THAT THERE WAS AN ENGINE FAILURE ON THE LT ENGINE MAKING THE ACFT VEER TO THE RT. MAINTENANCE REPAIRED AND FUNCTION CHECKED. GROUND RUN SYSTEM. SERVICEABLE.