Starter Question on a 94 530I

[TransMort]

Hey all, my daughters boyfriend just got a 94 530I.
While driving it he got a grinding sound shut it off and wouldnt start back up.
(im a GM Tech) so they call me up and i listen to it and determine that the starter gear isnt disengaging from the ring gear thus the noise.
He gets a starter, but the new one has only 2 posts on the solenoid while the old one has three. i put the starter in anyway and connected the batt. cable and the larger solenoid post, the car started 10 times in a row. so i taped up the smaller wire and reassembled the shields. i get a call an hour later sayig the car wont start. should i have connected the smaller post wire to the larger post. or just get a 2 post solenoid starter?? never had a no start condition before today and i want to try to get this settled.
Thanks
Transmission Mortician

[TransMort]

Daughter got home so i finally got the keys, Turned it over and the starter motor is just whining, not engaging the drive gear in the starter. one question though, what does smaller of the 2 solenoid wires do?
i get a crank signal to the fatter one but no signal to the smaller grey wire?
At least it is an easy starter to replace.

[witeshark]

You may wanna check the starter solenoid also.

[jimoreno]

You need to get the ETM (Electrical Troubleshooting Manual) for your specific year and model. If you search around you can find them. In the diagram for my car (1995 530i) it shows three connections to the starter so you might have the incorrect starter for the car.