Small Engine Troubleshooting Problems? Ask a Mechanic Now.
What is battery voltage? 13 + would be fully charged, less that 12.5 volts will not start mower.
There is a circuit breaker in the system, it may not be letting full voltage thru it. The fuel solenoid clicking shows there is some voltage to the keyswitch. There is also a 10 amp fuse, be sure it is good.
Solenoid on the starter? Remove spark plug and see if you can turn the engine by hand,
Engine may be liquid locked!
If engine turns, remove the starter and bench test it.
Yes, if starter is good.
Your starter solenoid is the noise under the seat. Solenoid may not be closing
Heat from a torch, to get nuts red hot, then remove! Without a torch, a person can split nut with grinder or cutoff tool.And what works with one may not work on the next one!