Murray rider stopped running,will not start when I turn the key,but with parking brake on and jump the silinoid it starts,I sit on seat and release parking brake it stops running again,when I'm not sitting on rider seat it runs,but I still can't start mower with key,and parking brake is on,and when I engaged the blades and release parking brake it stops running?

Well I thought it was the safety switch under the seat,but it wasn't,then I replaced other two safety switches,still wouldn't start,so I replaced the solenoid,and it fired right up,with the key,tks for your help.