Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Welcome to JUST ANSWER small engines, let me try to help you !! I don't know it all, but maybe together we can get you a satisfactory answer!
What is the battery voltage when you turn key to start? If it stays above 9 volts, battery , cables, and starter ok.. Remove the spark plugs and see if engine will now spin, may have liquid on top of a piston. If voltage drops at battery below 8 volts, battery , cables or starter is bad.
If no voltmeter, go direct to the starter solenoid, and jump the battery terminal to the single switch wire n the same solenid, and see if engine cranks.
OK, check the switch wire voltage from keyswitch to the solenoid, when you turn key to start. Do you get battery voltage to the switch wire? May be a bad key switch.
15 volts? at the starter solenoid switch terminal? If so, replace the solenoid!
If keyswitch sends voltage to the solenoid, and the solenoid does not close, solenoid is bad,
Any auto supply should carry a mower solenoid/relay.