94 taurus starting problem URGENT
I have a very interesting problem & I'm needing some help. Today I went to start my car & I got nothing...I just bought a brand new battery 2 days ago, thats not it. I tested the Alternator & thats doing fine. Tested the starter, thats fine. My dad came to put another battery in my car to get me home & started right up. Came home & put my new battery back in & tested it, works fine. So there is something that is blocking/stopping my car from starting sporatically. It seems like the next time this happens I will have to disconnect the terminals from the battery for 5 minutes & try to start it because my battery is not the problem. Is there something causing a ground or blockage enough to not start my car. I also have a brand new ECM in the car also, so I don't see it being that. Anything would be so greatful. Thank you so much in advace, anyone.