I started the engine in our '88 F150 V8 and it quickly started sounding like it was excelerating. I checked to make sure that the gas pedal was not stuck and nothing was on. Then it sounded like something popped and the engine stopped running all together. We have replaced the battery, checked the celenoid (I don't know if I spelled that right), and then replaced the starter. It's still not working and we hear the starter relay ping when turning the key but that is all. Battery is fully charged and the lights and radio come on but it won't turn over. What do we do next?