recently got a bronco as a gift, and she’s got a few things that need fixing. But the main one right now is getting her running. We bought a new starter as well as an ignition and was finally able to get the truck started, but when it starts the starter will not shut off… any ideas?

 

For starters, what year is your Bronco?
What engine is in it?
Is it a manual or an automatic?
It can be helpful for future posts to put your Bronco's information in your signature.

When you say that it won't shut off, are you meaning it's like you're still holding the key in the START position and cranking it? Or that it won't disengage from the engine and grinds after it starts?

The first would be an electrical problem. Either with your key switch or with the starter solenoid. Both can be diagnosed with a voltmeter.
To diagnose the key, pull the small wire off of the starter solenoid. It should read 0v, go to 12v when you put the key in the START position, and then drop back to 0v when you release the key. If it doesn't, and stays 12v, you have an issue with the key cylinder on the steering column.

A sticking starter solenoid is more likely. When the key is in the START position, it sends power from the battery down to the starter. Again, you can test this with a volt meter. The post on the solenoid going to the starter should only have 12v when you're starting it, and then drop back to 0v when the key is released. If it stays at 12v, the starter solenoid is sticking and needs to be replaced.


If the starter is staying engaged and grinding, it's possible you got the wrong one. There is a difference between the starters for an automatic and a manual. If you switch them up, they'll fit, but have issues with grinding/disengaging.

 

The first thing to check is the starter solenoid. Try this: put the key in the ON position (just before START), then bridge the connection between the two poles of the solenoid using an insulated screwdriver, if the engine turns and the starter disengages as soon as you remove the screwdriver, you've got your cause, the solenoid is getting stuck. If it's new, you can try tapping it with a hammer, they usually start working fine after some cicles getting stuck. Keep a battery terminal loose in order to be able to remove it quickly in case it's the starter motor the one getting stuck.

BTW, welcome to FTE!

 

I had the opposite problem. No juice from the starter relay. Replaced it and works like a charm