when they fail. However, a hose popping off under pressure does. First rule of diagnosis: Listen to the customer's description of symptoms. Second rule: Don't overlook the obvious. :-)
ps. I've had an air leak from a misaligned plenum gasket that prevented the car from starting before, so if one of the intercooler pipes/hoses or recirc. hoses popped off they would create a large enough gap to prevent starting. Not saying an air leak is definitely the problem, but would be the most obvious one to check first based on his description of events.
