You may want to follow Omegaman's advice on this thread. He puts the socket and breaker bar on on the nut, then hits the starter.

http://www.peachparts.com/shopforum/showthread.php?t=150588&highlight=harmonic+balancer+failure

AFAIK, there is no rubber part. Here is an exploded view of the crank and its related parts.

http://detali.ru/cat/MB/B03015000111.0051.gif

You need to ignore my earlier comment about rubber parts. I still have in my mind some image from this site of a large round metal object, loose on what I recall to be a crankshaft. I thought it was some kind of vibration damper or something associated with the nose of a 617 which had separated from its rubber components. Perhaps it was all a dream.

Well, I wasn't dreaming. There is a rubber part in there. Here's a whole thread on it. I'm linking to the page with the pictures:

http://www.peachparts.com/shopforum/showthread.php?t=58996&highlight=vibration+damper&page=5

HOWEVER, it doesn't look like a failed rubber part can cause your problem.

That is on the damper, separate from the pulley. It's not going to cause the pulley to turn independent of the crankshaft, even if the bonding material does fail. The pulley is bolted to the balancing disc with the vibration damper sandwiched in between.

Doesn't it almost have to be the woodruff key sheared? And I don't like the chances of the groove on the crank being left in good shape either......:eek:

That engine uses two dowel pins instead of a Woodruff key. See part #23 in post 17 above. (The Woodruff key shown is for the chain sprocket.)

Same concept though. If the engine runs, the only real possibility is that the pins sheared. Or they are "missing." Bad news any way you slice it.

Actually a fairly common problem. I had a 300d na that had that happen. It required a new crank (used).

I hope it is one of the less drastic problems for you.

Tom W

Ask me how happy I am that I'm not intimately familiar with this area.....:D
I'm just sorry that James sounds like he is gonna have to become knowledgeable about this. :(

No dream Kerry, it happened to my Father's Lexus, the rubber failed and it lost drvie to the serpentine belt, ... clever design that Toyota stuff.

^ It's actually quite common on other cars. our Volvo is similar design.

not knowing the exact layout of the engine, if the pulleys at the front of the crank can be removed, and those dowel pin holes are accessible, is there any possibility of drilling out the sheared off pins and replacing them with new ones? Just a thought.

Not really. The dowel pins lay parallel to the length of the crankshaft with 180 degrees embedded in the crank and the other 180 degrees embedded in the balancer. If they fail, they typically destroy the groove in the crank in which they reside.

But something seems odd about James' description of his failure. Am I correct in thinking that the timing notch into which he thought he could insert a screwdriver is on the harmonic balancer. If locking the harmonic balancer will lock the crankshaft, then clearly it is not free to spin on the crank and the dowel pins must be ok. This would point to sheared bolts but he says the bolts are still tight. Something doesn't make sense to me.
The only explanation I can imagine for his description is that the crankshaft is broken behind the dowel pins.

My point exactly. If the bolt on the nose of the crank is tight, and turning the pully when wrenched, the nose of the crank appears to be broken off. It has happened on this forum in the past year, an SDL, '87 I believe in GA, he was trying to sell it really cheap but I couldn't get there.