starter issues
 

I bought a new starter and i'm having trouble with cranking the engine over. what happens is when i turn the key in the start position, i hear a humming sound coming from the starter. i took it off to check the flywheel for any damage and all the teeth are there. the starter goes on smoothly, it's not crooked. i had the starter tested and it's good. any suggestions as to why this is happening?

Re: starter issues
 

What year and model Mustang do you have?

Re: starter issues
 

Actually, I solved the problem. It was the battery. I didn't have it fully charged. But I do have another problem with. Sometimes on real hot days my car shuts off. I think it's because I'm not getting enough air flow through the engine bay. I'll have that problem solved shortly but I just want to see what else could cause the engine to shut off. I've also heard that if the TFI module gets hot that it could mess it up, cause it to not function correctly.