SMOKE CABIN AND COCKPIT. FUEL DUMP RETURN LAND.

Narrative

SOURCE OF UNKNOWN SMOKE THICKENING IN CABIN AND COCKPIT ON CLB OUT OF LAX. DUMPED FUEL TO MAX LNDG GROSS WT. LNDG WAS UNEVENTFUL. MECHS FOUND OIL FROM APU IN THE AIR CONDITIONING DUCTS; APU HAD SHUT DOWN EARLIER (AUTOMATICALLY) DURING PUSHBACK AND #1 ENG START. AS RESULT ENG START WAS HUNG AND WE FOLLOWED OUR FLT MANUAL PROC TAXI OUT WAS HECTIC. WTS WERE LATE ETC; SO WE DISCUSSED THE APU AND ELECTED TO WRITE IT UP ENRTE (SINCE THE APU IS NOT USED IN FLT AND WE OFTEN FLY WITH DEFERRED APU'S)! OUR ERRORS; SINCE HINDSIGHT IS 20/20 INCLUDE: NOT RESEARCHING WHY THE APU SHUT DOWN. EXAMPLE -- APU OIL QUANTITY WAS NOT LOOKED AT. ALTHOUGH AS A CREW WE DECIDED NOT TO CONTACT SAM; OUR MAINT HEADQUARTERS IN SAN FRANCISCO; BECAUSE ARINC IS REQUIRED AS A MIDDLE MAN AND THE TIME INVOLVED CAN BE LENGTHY. WE WOULD AND SHOULD HAVE TAKEN THE TIME. A POSSIBLE SOLUTION FOR 'THE NEXT TIME' COULD BE TO CONTACT THE LAX MAINT; HOWEVER; THIS IS NOT OUR CURRENT COMPANY POLICY ONCE WE'VE PUSHED BACK. POLICY MAY NEED TO BE RECONSIDERED OR CHANGED BECAUSE THE TIME REQUIRED IN LAX IS MUCH LESS.