Replaced ignition switch...car still won't start. Need advice.
 

1989 Audi 90Q. Ran fine until I went to start it a few days ago. Key turns, fuel pump turns on, engine OK light comes on, etc but starter won't crank. Turn the key to crank - no click no nothing. Tested voltage at starter solenoid and not getting 8V at terminal #50 from switch when turned on. Suspect faulty wire but I find it hard to believe a wire would just fail all the sudden without any prior warning. Replaced ignition switch and still won't start. Solenoid and starter are fine because I can jump it at the solenoid. I checked the fuses and nothing blown. Am I missing something?

so no power at starter solenoid trigger wire?
 

Hmm... so the connector looks fine and isn't too rusty. Start tracing it back up... look for a dead spot (perhaps it melted or shorted out).

Then, pop the fuse panel cover. Look for the 'starter interlock relay'... the quattro cars don't have a starter interlock relay, but instead, a solid wire bridge (looks like a funky copper L). Pull that out with a pair of pliers. Make sure it's clean. When inserted, I do believe this should see 12V when ignition is in the START position.

(the interlock relay is for automatic cars... if in anything other than park/neutral, it tells the relay to not let the car start. On the manual cars, they assumed you were bright enough to be in neutral or have your foot on the clutch... hence the bridge wire.)

Try that and report back.

No power at the trigger wire. Tracing the wire tonight.
 

Thanks for the tip about the jumper piece. I'll test for 12V there.

Is there a switch at the clutch pedal?

jump out the starter, see if it starts without using the ignition

Already tried that and it works...starter and solenoid are good

Car was able to start with or without pedal depressed, so I'd say no.

Check wiring schematics for relay. Could be a relay has gone bad.

Relay sounds reasonable but there isn't one I could find in the starter system.

2nd... nope... only switch down there is cruise-control... and it's purely vacuum based...
 

you can start these cars without a foot on the clutch. No start-in-gear protection.