Lost sync help?

[dpstark2]

Hi all,

I recently converted my slant 6 Dart to MS3 fuel injection. This is my second MS3 car. I also have a '67 Charger with a 440 running MS3. Both use 36-1 tooth wheels on the crank and a Hall sensor. I don't remember the specifics of the sensor, but it is a gear tooth type I got from Digikey that is physically identical to https://www.diyautotune.com/product/hal ... on-sensor/. My Charger has no issue with this sensor. Both MS3's are using the opto input and have the same software settings.

My Dart loses sync about once every ten minutes. In all cases, the cause is identical. It shows an extra tooth about halfway between two teeth. The attached sync error logs show the failure at two different speeds and locations. Between the two, I moved the sensor wiring because I noticed I had run it right by all 6 plug wires. This did not make a difference. All grounds are to the same place on the head, just like my Charger. Other than this, the car runs fine and everything is working.

I have read about the noise filtering, tach period rejection, electrical noise, etc. I had no such issues with my Charger after going to the hall sensor. I don't know where else to go with this problem. I hope to borrow a scope and check the signal on the board, but that will take some time.

Other pertinent info: firmware 1.5.0, TunerStudio 3.0.28. MS3 controls a single coil. "Noise suppression" plug wires, but nothing fancy. Batch fired multi-port injection.

Any help is appreciated.

[Matt Cramer]

What are the dimensions of the teeth on that wheel?

[dpstark2]

I'm not sure. I can measure them later, but it's this wheel from DIY Auto Tune: https://www.diyautotune.com/product/8-1 ... -no-slots/

The teeth are about 1/8" thick. The description says they are 1/4" high and that seems about right from memory. I opened up the hole in the center on a lathe to fit a 3/4" bolt. I sandwiched the wheel between the pulley edge, a spacer, and a 3/4 bolt into the crank. This is different than my Charger setup, and I think the Charger even has the 6.75" wheel. I would think that bigger wheel would be better, but maybe that's not the case.

Here are some pics. The part number is visible. This shows up as a Littlefuse part on Digikey, but I believe it was a Honeywell part at the time.

https://photos.app.goo.gl/KsQdGbfe2l4wy7Z42

https://photos.app.goo.gl/NzWthUHuTCrLEW6A3

[Matt Cramer]

Try turning on the software noise filtering - a 40% tach period rejection setting may be what's needed here.

[dpstark2]

I'll give it a shot. Thanks.

[dpstark2]

All this turned out to me my fault. If one would read the manual closely, one would see the recommended input for a Hall sensor is the VR circuit. Turns out I did this on my Charger. For some reason, my memory said otherwise.

Setting the tach rejection period to around 45% also fixed the issue, but I'll stick with the "right" input unless something else comes up.