NSEU,
You're assuming there is automatic starter cutout. I don't knows about all Boeings but some 727s had and some didn't. Our NTSB has a nice report with pretty pictures about a MD-80, JT8D-217s, the start valve either didn't get fully closed or opened up on T/O. Shortly after T/O it decided it had had enough and left the engine. Easy to see where the starter was located because there is a large section of cowling that went with it. Since there was fuel and air and spark left behind, there were all the ingredients for a fire outside the burner cans.