It won't start when you turn on the key. I put in a new battery and starter.

I need to know model year? I looked at wiring for 1990 ford bronco. 5.oL engine.
The gasoline engine shows a starter relay that is not mounted to starter motor.
The diesel engine showed starter solenoid mounted to starter. I'm not sure which engine you have? They both have a starter relay.
I think your headed in the right direction, I need more info.

You may need to replace your starter. Most auto parts stores ( like Advance auto, Autozone, Napa, etc. Can load test your starter, testing for operation and amps drawn. If the starter has a small cylinder mounted next to it( that's the solenoid) You may want to try tapping on it after blocking both front wheels and as a helper turns the key. I don't suspect the solenoid as the starter is turning but the armature is not extending ( the winding noise). If tapping doesn't work, you'll need to disconnect the negative cable from the battery before removing the starter for testing. I suspect you'll find the starter is defective.
Hope this helps and thanks for using Fixya!!

If you hear a clicking sound but no joy on the starter, you may have a bad starter solenoid. Follow the positive cable from the battery, it should end up connected to the solenoid. The post the battery cable connects to should be adjacent to another post where the cable connected to that post leads to the starter, you can check by carefully crossing the two posts with a small screw driver or some other piece of metal to see if the starter will turn over, (be very careful not to touch any part of the body of the mower with the screw driver). if the motor turns over with the crossing of the posts but not with the key, then more than likely that is the problem. Replace the solenoid. NOTE: you do not have to have the key turned on for this test.

Hi! It sounds like a bad solenoid, or that you're not getting the 12 volts to the solenoid to engage the heavy amperage needed to turn thr starter motor.
When you say you bypass it,do you mean you are just crossing the large post of the solenoid with the battery cable connection at the starter?
When you turn the key,you should get 12 volts at least at the smaller post on the solenoid.If you have 12 volts there when the key is all the way to `start 'position,then the starter probably ought to be replaced.
This car being a 2000 is 13 yrs.old.Won't hurt to put a new starter on it.
don-ohio (:^)

check if 12v go on solenoid of starter when you turn key to start,mesure 12 v on starter when you turn key to start
if voltage drop to few volt,wire or connection are bad

Check all ground wires and make sure they are tight. Start at the battery, starter, solenoid switch.

DO you hear a clicking when you turn the key to start? Solenoid relay make a click sound when energized.
If the solenoid is not mounted on the starter motor then it will be near the battery
The key switch sends power to the solenoid. the solenid is a big remote controlled switch,and it takes power from the battery to the starter motor

did you check the starter solenoid their is one one the starter it's self but their should be another one under the hood near the battery, it should be round shaped with two post on it and it will be mounted on the side wall near the battery. If you put your key in and turn it to the on position but don't start it and take a screw driver and use it to cross the two post you can test it to see if it is bad. If when you cross the post it starts it is the solenoid! If not check for spark and fuel! If you check the solenoid and it is still good just let me know and I will tell you the next step you need to take!

check alternator output at the alt and at battery also put a test light on the starter solenoid at the little wire on solenoid see if it lights up when turn key ? possible positive or negative cables have good ohm checks but not carrying enough current ?

Sounds like solenoid on starter has packed it in Try crossing solenoid terminal (small wire on solenoid) to power feed on starter (End of battery cable) If nothing happens Remove starter & renew solenoid