I have a 1992 Ford Explorer that suddenly wont start. We were parked at a store the other day and it wouldn't start so we got a boost. On the way home we made another stop and my husband accidentally shut the engine off and had to get another boost. At first we thought it was the battery so we tried a newer battery, but after it sat for a few days trying a boost wouldn't help. What are the possible other reasons for it starting with a boost two times and now not starting at all? Thanks.