I'd suggest you might want to narrow down the problem a bit before tearing things apart. The question is: is the starter getting a correct signal from the ignition switch and not responding ?
One way to troubleshoot is to hot-wire the starter:
- make sure the car is in neutral, parking brake on, wheels chocked
- locate the small spade terminal that plugs into the starter... it's next to the big bolt and lug to the main cable that goes directly to the battery.
- pull the wire off, leaving the terminal exposed
- confirm that the car is in neutral, parking brake on, wheels chocked
- using a short length of wire bridge between the big battery connection on the starter and the small terminal on the starter... the starter should engage and the engine should turn over (hence the reason for neutral, parking brake, etc :wink: ).
If the starter turns over properly the problem is likely upstream at the ignition switch or the wiring between the ignition switch and the starter... corrosion at the starter itself is a common problem
If the starter clicks but doesn't turn over the problem is the high-current feeds (power and ground) from the battery or the starter itself. Start by removing the two big battery terminals and then the big cable at the starter and the big ground connection to the transmission... carefully clean and sand all four reassemble, and try the bypass trick again. If this doesn't work the quickest thing is to pull the starter and take it to a shop for further testing / rebuilding.
If you do replace the starter be sure to replace the bushing in the transmission... instructions on one way are
here. Bosch in particular will void your warrenty if you don't replace the bushing... it's under a lot of duress (particularly on a diesel) and can easily cause your new starter to bind.