...out.

New here but a long story, didnt use the car for about a week and the battery went dead, charged the battery and started the car, run for about 2 minutes at idle and very rough and died, would not start again.

Dropped the car off at the Audi workshop and they advised they suspect the crankshaft timing is out, probably due to the crank pulley key shearing off. The camshaft timing is correct they say. They did a compression test and it was very low, they say due to the crank timing been out. So the way I understand it is the crank turns the camshafts so how can the camshafts stay in correct timing if the crankshaft timing go's out, surely they work together.?

Or am I missing something here, can the crank turn and the pulley stays stationary.? Has anyone ever heard of this kind of issue, it all sounds very odd to me.

Any info to help me understand will be appreciated.

 

The crank uses a key to keep the crankshaft gear in place. There's a picture here. If the key sheared, it could be possible for the crankshaft gear to rotate independent of the crankshaft. Assuming the timing belt didn't jump any teeth, the camshafts would still have the correct timing amongst themselves (the valves in each bank would be in the correct positions as the camshafts spin not taking the crankshaft position into consideration). However, if the crankshaft gear moves from where it should be, your timing will be off a certain number of degrees and your valves will not open and close at the correct times (taking both the camshafts and crankshaft into consideration) causing a rough idle or not allowing your engine to run at all. Hopefully you didn't bend any valves.

 

Hi jeckel20003, fortunately it seems not, apparently the timing only went out by about 15 degrees but it was enough to stop the car from starting.

Your info was spot on, and from what I was told today the key didnt shear completely but the pulley was slightly rotated on the crank by about, as they told me 15 degrees. Luckily, I am told the car was just ideling when it happened or there would have been serious damage.

Just as a matter of interest, any idea what causes such an issue, the car has only done about 150,000 kilometres as its seldom used. I asked at the Audi workshop, but the workshop manager just sort of shrugged his shoulders.

 

this is absolutely true. however, i am not aware of any 1.8's, stock for sure, that have sheared the crank key. i am aware however of numerous occasions that the cam key has sheared. what im guessing the tech meant by saying that the cam could be on and the crank off of timing is that the cam matched tdc and the crank didnt.


idleing doesn matter. you could still seriously mess up your valves even while idling, which i am guessing is what happened. are you gonna try to fix this yourself? pictures of the timing marks on the cam shaft and crank shaft would help us determine what is going on. the timing on these motors can be off a little and still run, but you usually only run into that scenario after you have reimed the motor, say after a belt change. if this happened without retiming, which it sounds like it did, it isnt good. if the cam shaft gear sheared the key or the crank sheared the key, odds are your head has many bent valves

 

No I have left it at the Audi workshop, I am not confident enough to tackle something like this myself, it looks like a really major job to be sure.

The belt was changed by Audi at 120.000 kms as per the spec I believe, and it has run perfectly fine since then, the car is dead stock and not driven all that much anymore so thats why I was so baffled as to the reason for the key shearing (I am almost sure the workshop said crankshaft key had sheared). According to the technician the belt is fine, as that was his first thought.

I am told they will only know once everything is stripped down and checked if the valves are damaged, but the technician told me he doesnt think so as the degree things went out (about 15 degrees) isnt enough to cause any damage, which would only happen if it was 20 or more degrees out on the crank. Small margin for sure, but I am hoping sufficient.

Is it common to shear keys on stock motors with such a relitively low milage do you think, I am not sure I trust the car any more and am wondering if I should just get it fixed and trade it before something else serious go's wrong.?