CAN REPLACING A STARTER WITH THE WRONG STARTER CAUSE PROBLEMS

You keep replacing the starter motors?
The starter motor may be fitted incorrectly and isn't meshing with the ring gear properly.

It may be that ring gear - the teeth - on the flywheel are worn/damaged or even the wrong fit for the starter motor.

Another alternative is that the flywheel isn't torqued up correctly and consequently it - and the ring gear teeth - are out of line. However, I would have thought that an out of balance flywheel would also cause vibration problems. Your car runs okay?

Could be the wires on the starter solinoid are on the wrong terminals, or the starter is getting power from the wrong source.

You did not mention what the status of the car was when this happened (VERY IMPORTANT... DO SO NEXT TIME). If you were attempting to start the engine when this happened, your starter may have failed. Starters occasionally shunt and cause this. Try replacing the starter AND starter solenoid. Also, verify that your battery connections are good, and that the battery wires did not have a meltdown. If they are burned, REPLACE THEM as well.

my friend has a 1998 ford f150. he's replaced the starter twice in the last 3 weeks, both starters have the same issue: a broken bendix houseing. what would cause this? is it the flywheel or wrong starter?

Check your ground cable and battery connections. Body grounds will give problems. Check and see if starter is engaged into flywheel. also Low voltage will cause a problem with starter bendex locking into flywheel.One more thing is check starter ground,If starter is not grounding it will cause problems.

spraying can pit your pistons and cause untold problems beside starting---======bet fuel consumption is high,have the pump serviced before it turns into a new engine

Age most likly, High current draw resulting from wrong size battery cables, poor grounding of engine block to battery are a couple more problems. But most likly the age of the starter, they do wear out.

Get the starter checked. If the starter shorted out, it's effectively the same as putting a piece of metal between the two terminals of the battery and you know what that means! Ka-boom! Hope this helps!
Cheers, John

I can tell u that the starter was put togeather wrong, most likely the wrong started drive was used.

Check all connections including the lower ground from the motor where it connects to the k member. as for the starter not shutting off check your ignition it might be faulty heavy sets of keys over the years cause problems for them.