What was found
APU FAULT LT ON AFTER 3 START ATTEMPTS NO START. FOUND NO OIL IN APU. FOUND CRACK ON TOP OF GEN AT 1200 POSITION APU GENERATOR SHARES THE OIL SYSTEM AND RESERVIOR WITH THE APU. THE LINE AND APU SHOP HAS HISTORY OF GENERATOR HOUSINGS CRACKING IN THE SAME FASHION AS THIS EXAMPLE. OIL LEAKS FROM THE GENERATOR CRACK, DEPLETING THE SUPPLY OF OIL OF THE APU. THE APU WILL HAVE A "LOW OIL PRESSURE" PROTECTIVE SHUTDOWN. SUBSEQUENT START ATTEMPTS WILL BE UNSUCCESSFUL UNTIL THE OIL SYSTEM IS SERVICED AND THE ECU (ELECTRONIC CONTROL UNIT) FAULTS ARE CLEARED. THEREFORE, WITHOUT OIL IN THE SYSTEM, ANY ATTEMPT TO START THE APU AT ALTITUDE WILL BE UNSUCCESSFUL.