I have a 1989 F250 ..351 engine. have an 850 amp 12 volt battery. Voltage of battery is around 12 now and almost 13 with ac and lights on. AFter a long 70 mile drive the engine is hard to turn after it is just turned off after the 70 mile drive... that is after I turn it off and then try to restart it it is hard to turn when the engine is so hot. I believe this is cause of starter. If it is the starter what part of starter causes this when it is so hot? Or could it be hot ignition wires? When engine is cold it turns fine.