You might want to post this in Diesel Discussion. You'll get WAY more help there. This forum gets swamped with all of the political crap in the other forum.

If the starter spins slowly when you jump the relay, you could have problems with your power wiring (poor connection, bad ground, etc), a failing starter motor, or a low battery charge. You have checked the battery charge right?

Failing voltage regulators on the alternators are very common. If you get the car started, test the charging voltage to make sure your alternator is working properly. A weak battery will crank slooooooooooooow on a diesel.