You may have quit your job due to a change in your transportation to your employer.  If you always relied on your car and it is no longer working, you have to either buy a new car or rely on other forms of transportation to get to work.  Explain to the interviewer that you never had problems with the car until recently and that you are unable to pay for the repairs on the car.  If you do not live near public transportation, tell the interviewer that.  You may also live far enough away from your employer that public transportation may not make sense.  Explain what you have tried to do to get to work, such as carpooling or moving closer to the employer but based on your current situation these are not feasible for you or your family.