flywheel separating from crank?

[majicwrench]

I have seen a few engines that when shut off, will drop enough carbon on the valves that they will not seat, and the engine then spins over like it has no compression. (Honda's do this, among others)
You state quite clearly that the cams are not moving, so the above would not apply, but I trust you, or someone else, actually WATCHED the cams as engine is spinning??
Looking forward to the answer,
Keith

[HOLLYWOODSPIDER]

Great news. For me, that is. Most of you will remain unaffected.

The alternator is turning! That means no dropping the tranny or pulling the engine. The problem has been successfully narrowed to the timing belt drive pulley. Paul, you're a genius. Thank you.

Keith, I can see the back side of the cams from the driver's seat.
Dread set in the moment I noticed they weren't moving.

I can't tell you how relieved I am and how much less I am dreading tomorrow. Now to locate a pulley.

[ITA124]

Could a shear key just give out?

When an engine is starting the value of the breakaway torque is quite high. This is the effort required to get the engine initially turning. This is escalated if components have higher than normal friction. These can be rotating cams, aux pulley, seized vale, etc. You'll find out through systems deduction.

Then again, I could way off the mark.

Good luck

[HOLLYWOODSPIDER]

It turns out the shear pin is in tact. The timing belt drive pulley is what has failed.
I'm currently hoping really hard that the pulley died of old age and that the timing train hasn't developed a problem that caused the pulley to give up. The head was redone and the timing belt renewed less than a year ago. I'll find out tomorrow when I finally go out and begin repair.

[So Cal Mark]

the crankshaft toothed sprocket?

[pope]

Mark, I cant figure out where this is going either! There is more investigation needed before a positive answer is given.

But I am hoping for the best.

[HOLLYWOODSPIDER]

Mark- that's the part. The sprocket on the crankshaft that drives the timing belt. My crankshaft is turning (hence the alternator turning when the starter is engaged) but the timing belt/gears are not moving. In addition, there seems to be residue from the sprocket's failure sprinkled in the oily parts in that area. Not chunks, but a dark grey "crumbs". Is that sprocket plastic or fiberglass?

Are there any tips or tricks involved in crankshaft nut removal?

[HOLLYWOODSPIDER]

As Pope predicted, only actual disassembly would reveal the true problem.

Half of the teeth are missing from my practically new timing belt. I had the head replaced last november and a new timing belt was installed. Without removing the cover. The timing belt appeared fine and retained tension. When I pulled it off, almost every other tooth was missing, and all of the teeth in the area of the crankshaft sprocket were gone. The remaining teeth were more than 50% separated from the belt.

The markings on the belt are 19014601 674 024 D 302 060. No manufacturer. I think I got it from IAP.

I wonder if it was defective in manufacture or if the local guy installed it incorreectly. It's not greasy or anything. Could undertensioning cause this kind of damage? The valve cams and aux cam are all turning as they should. There doesn't appear to be any undue friction in the valve train.

[pope]

Not chunks, but a dark grey "crumbs".

This is just me talking without anything to back it up. Those crumbs are probably the belt grindings accumulating around the crank. I cant believe the crank sprocket is damaged in any way, this is one hunk of metal. My guess (and I cant back this up in any way) is the high torque starter caused this belt damage. I think the starter is stronger than the belt would allow in this instance and just shredded the teeth on the belt, before the turning of all the parts of the engine could catch-up.

[So Cal Mark]

I'd say the belt was probably OVER tensioned from the descriptions of the failure. The belt failure wasn't caused by the starter. Most timing belts fail exactly like that; when the engine is initially cranked. As soon as the area with the worn teeth hits the crank pulley it stops turning. Since the belt has missing teeth all around, it was on the verge of failing. The old square-tooth belts that Fiat used commonly suffer from sheared teeth. The reason most cars now have timing belt life of 90000 miles is due to the change in belt/pulley design; they now have rounded teeth

[HOLLYWOODSPIDER]

In addition, the failed belt was of far inferior quality to the new Gates belt I installed Monday. The reassembly went great and the car started right up once the new belt went it, no damage to valve train. Whew!

Is it possible to over-tension the belt since the tensioner spring is the one built in to the engine?

The new starter doesn't turn the engine too much faster than the original, maybe 10% faster. Not so much that it dould seem to be a detriment to thre timing belt. I think low-quality belt was the problem.



Anyway, it's great to be back behind the wheel and for the cost of just a $25 belt and a few hours work. Since the repair was so inexpensive and I had already gotten out of work for the day, I bought and installed a new stereo, which I can actually hear while the car is moving.

[So Cal Mark]

that's great news! glad it all turned out okay. The benefits of a free-wheeling engine sometimes are overlooked. In the constant drive to raise compression, that feature is lost.

[HOLLYWOODSPIDER]

This experience has taught me the value of both the Free-Wheeling engine and AAA Premium Roadside Service. The lack of either one would have cost me hundreds of dollars.

[pope]

Glad things ended well.
I agree that you would have to go out of your way to over tighten a belt.
Although the new starters spin a little faster, the torque behind the spin is 30% or more higher than original. I think they may weed out suspect belts faster.
Most engines in America are chain driven crank to cam. Much stronger than belt drive. What might help is buying the extra wide belts.

What a relief.