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912 ignition sprocket chafing the engine


Finlandese

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What the hell is going on over here? The sprocket is loose but the bolt doesn’t move. The washer below the bolt is loose. You can turn the shaft about 20 degrees, even though the sprocet is held in place by the timing belt.

Help!

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Please detail how you found it.  Did the engine stop running?  I assume you're not trying to start it!  I imagine you're looking at sprocket failure, and probably damage to your oil pump shaft.  Do not even think of turning the key.

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British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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49 minutes ago, Sparky said:

Please detail how you found it.  Did the engine stop running?  I assume you're not trying to start it!  I imagine you're looking at sprocket failure, and probably damage to your oil pump shaft.  Do not even think of turning the key.

Had trouble starting the car and when it started, it had an intermittent jerk while driving, that felt like it was ignition related. Noticed that the distributor cover had come loose. After putting it back on car started normally, but now my friend, who was observing the start in the engine bay, noticed a tapping sound coming from the front of the engine. After a while we noticed the chafing ignition sprocket and shut off the engine.

I remember hearing a similiar sound previously. I assumed it was the hydraulic tappets, but of course I should have remebered that the engine does not have them. I added oil and the sound went away.

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Do not start the engine.  That sprocket must be removed for investigation, but first I'd manually turn the engine to ensure cam timing hasn't slipped with resultant engine damage.  You'll need a new sprocket, possibly repair/renewal of the oil pump/distributor drive, and of course a new cambelt. 

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British Fart to Florida, Nude to New York, Dunce to Denmark, Numpty to Newfoundland.  And Shitfaced Silly Sod to Sweden.

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8 minutes ago, Sparky said:

Do not start the engine.  That sprocket must be removed for investigation, but first I'd manually turn the engine to ensure cam timing hasn't slipped with resultant engine damage.  You'll need a new sprocket, possibly repair/renewal of the oil pump/distributor drive, and of course a new cambelt. 

Thank you for your advice. We checked the timing and it was still correct. The cam markings lined up perfectly at the TDC. 

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  • 2 months later...

Trying to get the oil pump off. All bolts are off, timing belt, distributor and the oil cooler is off. Why isn´t the pump coming off? More force?

After that, the mystery of the coolant lying on the block…

 

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Other than the 9 M8 bolts there is nothing else holding the pump to the block.  There is an M6 hole at the pulley end of the casting just above the block - check nothing is attached - I don't know what it is for.  Lever it up carefully if all bolts are out, but obviously don't damage the mounting surfaces.

Pete

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The mystery is beginning to unravel… The point of failure beng the dear PO who had not cleaned the sprocket bolt hole and therefore thought that the bolt had been tightened all the way. It was not and the play had started to eat in to the shaft, sprocket and the wedge.

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It seems that I have an Esprit 907 oil pump with an Excel sprocket. The fit to the auxiliary shaft is quite loose. Is that because these parts are mismatched, or due to the wear of loosely fitted sprocket? Does 912 sprocket with to the 907 auxiliary shaft?

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They should all be the same.  Must be wear.  Are you planning to continue using the damaged auxiliary shaft?  You could always get a new keyway cut in it if the diameter is still OK.  The sprockets are hard anodised apart from the bore making the bore relatively easily damaged.

Pete

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  • 3 weeks later...

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