strange problem

Have a model 917.258523 with a 15.5 Briggs. It started out not turning over with the key but I could jump the solenoid. I found that I had 2 safety switches that was not working so I bypassed them. Now it turns over with the key but won't fire when turning but when I let up on the key it starts to fire till the motor stops turning. I have never had anything like this happen before. Please help