As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAILED TO START THE STARTER LIGHT STAYED ON FOR 30 SEC THAN APU FAIL MSG POWERED UP. 2ND START SAME OUTCOME. RAMPER WAS REPORTING SMOKE FROM THE APU. COMPLIED WITH E&ACC BOTH TIMES. ( APU INOP ). REMOVED FROM SERVICE. R&R BOTH START FUEL NOZZLES IAW Q400 AMM 49-30-19-000-801 & 49-30-19-400-801. OPS CHECK GOOD. CLEAR MEL. AIRCRAFT RETURNED TO SERVICE.