Q: My car won't start - 1999 Ford Taurus

There is an important distinction to be made here. Is your car not cranking or is it cranking but not starting? Most likely you have a bad connection and a jump start is adding additional voltage to overcome it. Either this or the battery is not capable of supplying enough current. The only way to test the current capability of a battery is with a carbon pile, that is, a load tester.

If you are using the key to start the car when you jump it, then it is not a fuse. I would first begin with load testing the battery. If this checks out, you will need to locate the bad connection in the starting circuit. Keep in mind, what looks like a good connection to the eye is not necessarily a good connection to electricity.

Locating a bad connection can often be done by attempting to crank the motor for up to thirty seconds. Go under that hood and feel the connections at the battery posts, the battery cables, and the connection at the starter. If any of these connections are hot, it is a poor connection and it will need to be cleaned and tightened.

I recommend having a certified mechanic, such as one from YourMechanic, come to your location to determine why the car is not starting and suggest any needed repairs.