help with TFI and spark cut/2 step

[pacwest]

I am far more a welder and fabricator than an electrician. And installing my MSII has brutally shown this. MSII, 2 step/launch control/ stock tfi, stock coil. 2300cc turbo.

Here is the stock wiring diagram for my car.




Now I think if i wired it like below it would run the timing right but I'd kill the coil after a couple minutes and there would be no tach input to the dash. I need to keep the magic smoke INSIDE my coil and wiring.




How do you wire a TFI for spark cut and a stock Ford coil and a stock tach? I'm a schematic kind of person. I've searched a bit and came up short. Everyone uses an MSD and the MSII tfi page (http://www.megamanual.com/ms2/TFI.htm) makes no mention of spark cut.

[Matt Cramer]

Getting TFI to cut the spark isn't all that practical - it's designed to keep sparking if it loses the signal. You'd have to control the coil directly from the MS to get a spark cut.

[pacwest]

As you can see in the second diagram that's indeed what I've planned. I wired it this way and I indeed have no tach and the coil fried.

[Matt Cramer]

You could wire the tach to the coil negative terminal.

What settings were you using for direct coil control?

[pacwest]

Apparently I had basic trigger but somewhere in the backup situation I loaded something with EDIS defaulted. EDIS signal would kill my coil.

I'll wire the tach to neg and switch to basic trigger and JS10. What does the dwell need to be for spark cut TFI?

[Matt Cramer]

That is going to depend on the exact sort of coil you are running; when you control the coil directly the TFI is more or less irrelevant.

[pacwest]

Matt you've been a great help. Thanks.

I wanted to keep the TFI in case I had to pull the MSII and put the eec in to pass emissions. Seems sorta redundant if I can't even get it running at this point. the more I read the more I'm convince that if you can get a decent timing table in their and let it learn you'll get a goos stoich pass on a sniffer.

I may just look at an alternative for spark cut and delete the TFI. I have a spare MSD box I could use perhaps.

[pacwest]

If any Merkur owners are interested, this is the proper way to do it: