Broken crank trigger sensor and plate while driving

[1g8420a]

I recently finished a stock rebuild of a 97 GST with 7 bolt engine. I had a small amount of setbacks after all those the car was running almost flawless (no codes Idle was great throttle response was good etc.) then as i was coming to a stop i heard what i thought was a belt getting chewed up then the car shut off..

This is what I found. The Crank trigger plate is bent. and the the angle sensor is destroyed. Pictured below.. My major question is why and how dose this occur (the sensor was still on tight when i pulled it off.) thanks for any advice or help.

 

[97gsxIA]

If you didn't find a foreign object in the timing cover when you took it off...

Somewhere along the line of installing the balance shaft belt/crank sprocket or timing cover you or someone else must have bent the trigger plate. maybe not enough to take the CAS out right away, but enough where some engine vibration got it close enough to the CAS and the rest is as they say.. history.

EDIT: Just saw your balance shaft belt isn't even on. Did you intentionally not install it?

 

[TSiAWD666]

For what it's worth my track car had similar occurrence with only a few thousand miles on the car and three track weekends. On the fourth track weekend in my first hot session's first hot lap I broke late as I was passing a slower car (and totally misjudged braking distance due to me being on the inside of the turn) and when I dropped off the track the car died, and wouldn't restart. Ended up the trigger plate had been hitting the crank position sensor. We found this of course by disassembling the timing belt cover and looking at the sensor. We didn't pull the plate to inspect it but we found at the time we could bend it slightly to get it to not hit the sensor. I later contact Marco at Magnus Motorsports, who built my engine, asking him if this was indicative of crankwalk and he directed me to measure the end play. My end play was just under the service limit of .0098"? I forget the exact limit. I told him what it was at and he said if that's the case then it's more likely a case of a deformed plate because it would take a lot more crank play to normally allow the plate to hit the sensor. He said sometimes the plate can get bent ever so slightly during install and he's seen it happen before. Since that on-track repair my car's been driving to and from I think six more events without any issues (knock on wood).

So with all that said, check your crank end play to see where you're at. You could have a deformed plate like mine supposedly was, or you might have a crank walk issue.

edit - per 97gsxIA's comment about a foreign object, that is also a possible cause. Hopefully your engine's wearing its full timing belt cover (and dear lord people, please do not spout anecdotal nonsense of how you have run XXXXX miles without one...).

 

[1g8420a]

The balance shaft pulley I installed for no particular reason the balance shafts are deleted..I guess the only thing I can think of is that the timing cover was not on. Earlier that day I checked the timing and re rtv'ed the oil pan. So maybe a foreign object would be a good assumption .. ill look into crank end play as well that thought did cross into my mind as well. I did have the motor machined at a local reputable machine shop.

 

[97gsxIA]

Normally I would see those bends (in those specific locations) on the trigger plate from someone trying to force a balance shaft belt around the trigger plate to get it behind it.

As TSiAWD666 said, end play (crank walk) is a possibility, but one could assume other symptoms would need to be present in that case.

Also... I cant tell with the picture.. is the bevel on the trigger plate facing outwards or inwards?

The incorrect orientation of the trigger plate WILL take out your CAS... amongst other timing issues.