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I went through a similar issue. I had a billet 24x wheel installed on my Eagle crankshaft. Also using Holley EFI. Anyway, the fucking thing would not start and was slipping in and out of sync while cranking. I was using the factory crank sensor, truck has less than 20k miles on it. Anyway, before tearing into complicated shit, I went to autozone and bought a replacement crank sensor. Threw it in and the thing fired right up. I then starting having issues with it loosing signal at 6500 rpm in boost and the ecu freaking out.

When LME installed the wheel on the crankshaft, it had a run out of .025". They told me that while they typically shoot for a better number than that, they assured me that it was well within an acceptable range and should work fine. Well, I later found out that .025" of run out is way on the high side. I chalked up the no start issue to be that the two crank sensor I had where just different enough for one to work and not the other. However, once I got into boost and 6500 rpm, the crank started flexing enough that nothing would fix it. Instead of pulling the motor down to find someone competent enough to install a new reluctor wheel, I just went to an external 4x flying magnet set up and all has been well since. The reason why I'm telling you this, it that I have seen first hand that a reluctor that is just on the verge of being out of spec that it can respond differently to different crank sensors.
 

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Could I have a glitch in the firmware update?
Not if the problem happens almost every time under higher boost. It seems something may be flexing just enough to render the crank sensor out of range.

Checked air gap it's .080/81.
I don't know what it's supposed to be on an LSx application, but that sensor air gap seems excessive to me. Probably why some crank sensors work and others don't. I'm curious to read what others think.

When LME installed the wheel on the crankshaft, it had a run out of .025". They told me that while they typically shoot for a better number than that, they assured me that it was well within an acceptable range and should work fine.
Someone should've been fired for that degree of incompetence! .025" radial run-out? What were they thinking? Some spark plugs are gapped that much! When I custom built my 60-2 crank trigger kit, I contacted the Cherry Engineering Department, and was pleasantly surprised to read their response, which stated that .005" of radial run-out was acceptable.
 

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I just pulled a fact. crank out of a 5.3 (24 rel.), the engine is still on the engine stand, I can drop the crank back in and put the sensor back
in and meas the air gap if you want
 

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OK, I thru the crank and sensor in and I meas. .027 air gap-so you are either not getting the sensor in all the way due to dirt or something where the
sensor jams, or something else-the crank throw next to the rel. is close to even with it, so if the rel. was any smaller the throw would be closer than
the rel.
I spun the crank and checked it in several places, the readings were all the same-not sure if there is a tol., but .027 compared to .080 is pretty wide.
 

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OK, I threw the crank and sensor in and I measured .027" air gap.
Thanks, I thought the sensor air gap should be tighter, like that. Something isn't right (reluctor, front cover, gasket, shims, etc.).
 

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Discussion Starter #28
Awesome, thanks for the info, I checked it with no oring seated as much as possible, I put a ball of clay on it without the oring slid it in pulled it back out cut the clay and measured it

I googled ls1 cranks sensor air gap and found this article related to bs3 with an external trigger wheel, they recommend .045-100 with an optimal .080
Not sure what Gm ideal gap is with their sensor. If I need to tighten the gap, it sounds like it's Goana be a pain
http://bigstuff3.com/pdf/Modifying_LS1_System_to_use_an_External_24_Crank_Wheel.pdf
 

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That Big Stuff sensor is apples to oranges compared to GM 24 tooth. The 24 tooth a finicky bastard in my experience. Sensor is really two sensors in one package I think with a circuit inside that figures out what to output to PCM. The "24 tooth" wheel is two offset wheels put together, never liked them.

Some info here... seems Callies has troubles with them too-

http://www.yellowbullet.com/forum/showthread.php?t=602348
 

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Not if the problem happens almost every time under higher boost. It seems something may be flexing just enough to render the crank sensor out of range.


I don't know what it's supposed to be on an LSx application, but that sensor air gap seems excessive to me. Probably why some crank sensors work and others don't. I'm curious to read what others think.


Someone should've been fired for that degree of incompetence! .025" radial run-out? What were they thinking? Some spark plugs are gapped that much! When I custom built my 60-2 crank trigger kit, I contacted the Cherry Engineering Department, and was pleasantly surprised to read their response, which stated that .005" of radial run-out was acceptable.
Shit man that was only half the story. I stood there and watched while this was going down. The wheel I ended up with (with .025 runout) was the second attempt. The first wheel the guy installed had a similar run out. I watched the guy grab a brass drift pin and big hammer to beat the thing into submission. He put the drift pin right on one of the teeth and it folded the tooth over on the first hit. I'm not the kind of guy to be standing in a shop (that is not mine or where I work) and start telling someone how to do their job. So, I just shook my head and watched him grind the welds down and press it off so that the second one would go on. He then proceeded to use an oxy/acy rig to heat the new wheel to go on. He basically held the torch (which was tuned up) on one part of the wheel to heat it up to ease the install. Of course that warped the wheel. I still am standing there, feeling like it is not my place to say anything. Well, sure enough, he gets it on, chucks it up in the lathe and measures run out to .025". Knowing he fucked the last one up, he just told me, it'll work fine.

When I left, I remember asking the guy in the office (owner) how long that person had been working there and he was like "Oh that guy has been here for a while. Good guy. Graduate of SAM".

Needless to say, they will never touch anything I do again. If your not aware, this issue caused me major headaches trying to diagnose the problem when the ecu would glitch out. I even had Holley involved. The problem was that I pulled the motor out of the truck. Took it over to the school and we threw it on the dyno without the blower. Of course, it would make 7500 rpm pulls without issue (the crank wasn't flexing), but at the time and because of that, everyone, including Holley was convinced that it was a wiring issue/glitch in the truck that was causing it. 6 months later and as a last resort we did the external 4x wheel and the problem went away.

People ride LME's nuts, but what nobody sees is anytime they fuck something up, it is never made public (which is quite often I hear).
 

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Not sure what GM's ideal gap is with their sensor. If I need to tighten the gap, it sounds like it's going to be a pain.
IF your radial run-out is good, no need to remove or touch the crankshaft or the billet one piece 24x reluctor.
Either mill down where the crank sensor mounts to, or mill down the mounting pad of the crank sensor itself.

Or, do something like what bigd427w mentioned above.
Fabricate a Hall-Effect crank sensor mounting adapter:
http://jonkensy.com/gallery/albums/userpics/10001/hall_adapters1.jpg
http://jonkensy.com/gallery/albums/userpics/10001/hall_sensor_final1.jpg
This adapter provides a fixed mounting point, but with a threaded Hall-Effect geartooth sensor, for easily adjusting the sensor air gap.
I use the same Cherry GS100102 Hall-Effect stainless steel 12mm x 1 threaded geartooth sensor for my custom 60-2 crank trigger kit.
Holley EFI 554-124 is a very similar Hall-Effect stainless steel 12mm x 1 threaded geartooth sensor for custom work (Instructions).

Again, if your radial run-out is good on the reluctor, I wouldn't disassemble the engine to fix it. You don't have to use the GM LSx crank sensor.
 

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Since I have a block on the engine stand, i'll look into the hole and look at the sensor and see if something could move it closer-the sensor seats in the block with a good solid stop, so
should be pretty ops. it is seated
 

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I put together some pics, I think you can arrow thru them-where the sensor bottoms in the block the hole is tapered-I imagine the seating rib could
be cut down, put a slight bend on the steel mtg. tab to allow the sensor to go further in-I guess there could be some man. tolerance in the blocks that
cause this, since GM didn't build these for high RPM and boost, lol
I would prob just take a few minutes, mod. the sensor and bracket see if that cures it-I would hate to mess with mine in the car, starter, down pipe, etc, lol

 

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I imagine the seating rib could
be cut down, put a slight bend on the steel mounting tab to allow the sensor to go further in.
Personally, I wouldn't touch (modify) the engine block, crankshaft or reluctor (IF the redial run-out is good). I'd try to drill & tap an M12x1 threaded hole right through the center of the GM LSx crank sensor, and install the Cherry M12x1 Hall-Effect geartooth sensor. If this crank sensor machining isn't possible, fabricate an aluminum mounting adapter like I linked in post #31. I would fix this problem on the workbench (crank sensor), not on the engine.
 

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Regular cherry sensor won't work because 24X wheel has teeth overlapped. Would have to be two small sensors, one to read each wheel and a decoder circuit....
What? Isn't the LSx crank sensor one Hall-Effect geartooth sensor?
 

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