Cleaning up a tach signal

[LR Max]

Good morning Everyone,

I'm looking for guidance on cleaning up my tach signal. Backstory: MS1 V2.2 (originally fried it b/c I'm running low impedence injectors, but installed a DIY flyback board kit). Extra code. Currently running fuel only. Vehicle ran fine before I started my EFI swap. Running a 1 injector TBI setup. Getting my tach signal off the coil negative.

Attached is my cranking data log. As you can see, the tach signal *sometimes* looks good, but then goes into a square signal. I checked and my D5 and D8 are installed on my board (not jumpered).

Any other suggestions on cleaning up my tach signal? I think this is what is causing my no-start issue.

Also I did put the MS1 on a STIM last weekend and everything looked good.

Also possibly linked, every once in a while I get a setting configuration error (fuel pump then cycles). Wondering if I've been messing around inside the controller so long that I've corrupted something? Wondering if I should reload my firmware.

Any suggestions would be appreciated. Thanks!

[LR Max]

Also wanted to add, I did put the timing light on the distributor. When cranking, I do get power to my spark plugs.

Also on my V2.2 board, I have a diode installed in D8, but it is NOT jumpered. Should I jump D8?

[slow_hemi6]

Being a TBI you should be able to see if it is injecting fuel when cranking. The log shows it is getting a cranking rpm and is commanding a pulsewidth. It should at least be trying to start if it is getting enough fuel.

[DaveEFI]

Looking at your log, your cranking RPM - judging by the battery volts - seems to be jumping all over the place. From about 30 rpm - which I'd guess is not correct - to about 270 rpm.

I'm wondering if your flyback board is wired in such a way as to interfere with things. Try unplugging all the injectors and do another cranking log, and see if you get a stable tach signal. Even with a V3 board, you sometimes need to modify the flyback circuit if you get interference to the tach signal from it.

[LR Max]

So, plot thickens.

On a whim, I replaced my coil. Boom. Clean tach signal. Engine Lit right up

However...of course, it can't be all unicorns and rainbows.

My original coil had a resistance of 3.0 ohms. Since its a 4 cyl, this is the correct coil resistance. My "replacement" coil has a resistance of 0.6 ohms (its off a V8). So while the lower resistance coil provides a cleaner tach signal, I run the risk of burning up my ignition components. So either I can have a usable tach signal...or use the correct coil for my 4 cyl.

With this information, what does everyone think? BTW. Thanks for all of the help so far!