As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ENGINE NR 1 FAILED TO START W/IGN-L. START SUCESSFUL W/IGN-R. GROUNDED-YES. PERFORMED B737-800 FIM 74-21 TASK 806, NO FAULTS FOUND. AS PRECAUTION REMOVED & REPLACED NR 1 ENGINE L IGNITER PLUG, REF B737-800 AMM 74-21-02. PERFORMED IGNITION SYSTEM AUDIBLE TEST, REF B737-800 AMM 74-00-00 TEST PASSED. WITH IGN L SELECTED PERFORMED NR 1 ENGINE START, REF B737-800 AMM 71-00-00. OPERATIONS CHECK GOOD. NO DEFECTS NOTED.