Just wanted to throw this out there for future reference and start some discussion on the topic following my more than week long befuddlement following my car dying on the highway.
1. This part can fail on M42s, not just M20s.
2. When it fails it may not damage the engine at all.
3. If on the highway the car will lose all power and stall in less than 10 seconds. Feels like a spark cut for obvious reasons.
4. Once you verify fuel and spark are occuring you will notice that the timing marks in relation to the cams are off.
After that it was a matter of troubleshooting. I went through every sensor, I swapped parts then I discovered that with the FW locked the crank wheel was disagreeing with the flywheel. The cams still showed TDC1. This is where I went wrong when I adjusted timing to suit the crank wheels indication of TDC1 assuming the chain had somehow jumped without noticing the horrific crunching, grinding engine death noises that would have followed. I then went down the wormhole of trying to adjust timing to an effectively floating crank wheel. You should do the following instead.
5. Rely on the hole in the FW as your correct TDC1 reference.
6. Confirm that TDC1 is correct with a screwdriver or similar on piston 1. Check that the cams agree with TDC1 (rear cam flats with dots flat, first lobes pointed up ~45 degrees at each other).
7. Look at the damn crank trigger wheel. Jiggle it, turn it by hand, marvel that it's now two pieces.
8. (Optional) Insert epithets now.
9. Find a used trigger wheel as new ones run north of $600.
10. Fix the issue and continue motoring.
I'll add pics of the broken part as soon as I have it off. Astounding that this failed as I have heard on maybe one or two occurrences on M42club. Not that it probably matters, but this only happened after I decided to run with a 4.45 differential the week before.
1. This part can fail on M42s, not just M20s.
2. When it fails it may not damage the engine at all.
3. If on the highway the car will lose all power and stall in less than 10 seconds. Feels like a spark cut for obvious reasons.
4. Once you verify fuel and spark are occuring you will notice that the timing marks in relation to the cams are off.
After that it was a matter of troubleshooting. I went through every sensor, I swapped parts then I discovered that with the FW locked the crank wheel was disagreeing with the flywheel. The cams still showed TDC1. This is where I went wrong when I adjusted timing to suit the crank wheels indication of TDC1 assuming the chain had somehow jumped without noticing the horrific crunching, grinding engine death noises that would have followed. I then went down the wormhole of trying to adjust timing to an effectively floating crank wheel. You should do the following instead.
5. Rely on the hole in the FW as your correct TDC1 reference.
6. Confirm that TDC1 is correct with a screwdriver or similar on piston 1. Check that the cams agree with TDC1 (rear cam flats with dots flat, first lobes pointed up ~45 degrees at each other).
7. Look at the damn crank trigger wheel. Jiggle it, turn it by hand, marvel that it's now two pieces.
8. (Optional) Insert epithets now.
9. Find a used trigger wheel as new ones run north of $600.
10. Fix the issue and continue motoring.
I'll add pics of the broken part as soon as I have it off. Astounding that this failed as I have heard on maybe one or two occurrences on M42club. Not that it probably matters, but this only happened after I decided to run with a 4.45 differential the week before.
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