The engine is in a John Deere 160 lawn tractor, but not sure that makes any difference. Mower died on me the other morning after I had started and stopped it 4-5 times. It was getting harder to start with each subsequent start. Battery tested dead, so I got a new battery. It has an electric start, a riding mower. When the battery is hooked up, it sends current and a whirring sound begins, and does not stop until I unhook the battery. I replaced the solenoid, and it does the same. Also, this occurs with key in off position, and it makes no difference if I turn the key to on or off. The ignition key does absolutely nothing when I turn it back and forth from on to off. Today, I cleaned the contacts in the ignition, but still the same. I am wondering if that whirring sound is the starter, which is now defective in some way. Or, what about the ignition coil? I appreciate your help on this.