1998 Dodge Ram 1500, 5.2L, AT, 149K mi won't start. Won't crank, just a single click when turning the key. Other electrical items (windows, radio, lights, etc) seem to work ok. Pulled battery and had it tested. Tested good. Even swapped relays of like type in fuse box, with no change in symptoms. Same symptoms when attempting to jump start. Any ideas?

the crank is in the center of the engine towards the bottom, it is held on by a larger bolt, 19 to 22 mm DO NOT REMOVE IT just simply put a breaker bar on in and turn it clockwise, all you are doing is verifying that the engine has not seized, turn it aabout one revolution. it will be a bit hard to turn but not imppossible, if it turns you likely need a starter motor. if its the starter you here one single thump when the bendix engages starter to flex plate but starter drive is not spinning, replace the starter the crank is in the center of the engine towards the bottom, it is held on by a larger bolt, 19 to 22 mm DO NOT REMOVE IT just simply put a breaker bar on in and turn it clockwise, all you are doing is verifying that the engine has not seized, turn it aabout one revolution. it will be a bit hard to turn but not imppossible, if it turns you likely need a starter motor. if its the starter you here one single thump when the bendix engages starter to flex plate but starter drive is not spinning, replace the starter