1. make sure battery is fully charged with good electrolyte levels. Substitute in a known good battery if unsure.
2. check and clean all battery and solenoid terminals, remove any corrosion with wire brush or file.
3. check for good start/no start
4. if nothing has changed, use a set of automotive booster cables to diagnose. Disconnect engine cables from battery first.
5. connect booster cables to battery terminals and a good ground in the powerhead area.
6. briefly tap the starter pos terminal with the booster cable pos. Starter should turn. If no, starter is faulty. If yes, check to see if the dog gear on the starter is climbing the shaft and engaging the flywheel to turn the engine.
7. if starter is motor is spinning but the gear is not turning flywheel, lubricate starter shaft and/or tap to free a frozen dog gear mechanism.
8. if starter is turning flywheel via booster cable, starter is good. Problem is in solenoid or wiring.
9. tap booster cable pos on solenoid pos input terminal - this is the same terminal your pos engine cable is connected to. If engine turns, this indicates wiring problem from key switch to motor.
10. if motor does not turn, solenoid problem is possible. Try tapping booster pos on the solenoid output terminal. If motor turns, solenoid is faulty. If motor does not turn, fault in connection from solenoid to starter is indicated.
Starters and solenoids are easy and inexpensive to replace. Just follow these simple diagnostics first, no sense in replacing parts unnecessarily. Remember, the most likely cause of electrical problems is dirty/corroded terminals causing bad grounding. Check and clean everything thoroughly, and use a dab of dielectric grease on each connection as you re-make it. Stay away from the control unit and ignition key until you're certain this is the location of the problem. These units are usually well sealed and are only rarely the source of connectivity problems. Carefully examine the cable between the controls and the engine cowling. It's possible rodents have damaged it over the winter.
