EDIS wiring question?

wes kiser · Post by **wes kiser** » Sat Apr 15, 2006 5:56 am

Looking at the wiring diagram, both the EDIS modules 12v + and the coil packs 12v+ are hooked to a switched source. I am putting EDIS in my mustand that originally had tfi. I noticed that the 12v + wire that is attached to the coil packs is substantially thicker than my existing coil or modules switch power. Since the module grounds the coil packs, would it be ok to run the coil power straight to the battery, and then pick up the module with my existing circuit. This would be a very clean and easy solution, and the only reason I could think of this not working would be if the module grounds the coils whent he power is off. Can anyone think of a reason not to try this?

Jim · Post by **Jim** » Sat Apr 15, 2006 7:05 am

That's the way I do it .

Get a waterproof inline fuse holder , the kind that has a rubber cap that
goes over the fuse , connect it directly to the positive battery terminal ,
then run a wire directly to your coil pack .

The Module must be switched with the Ignition Key , check to make sure
that where you connect the module power wire is hot while cranking .

I had done this with my injectors also , but it turns out that the
"Current Limiting" and "Flyback" and "PWM" curcuits in MS will draw
enough power when "OFF" to kill the battery .

YOU MUST USE A FUSE , an unfused wire can start a fire !!!

...................Jim

wes kiser · Post by **wes kiser** » Sat Apr 15, 2006 9:17 am

Thanks, I was either going to use and inline fuse or a fusible link. What size fuse are you using? I was thinking a 12 gauge wire and 15 amp fuse. I thought the easiest way to do this would be to power the module off my existing coil circuit, so that is definately hot in crank.

Jim · Post by **Jim** » Sat Apr 15, 2006 9:33 am

I run a 15 amp fuse , it's not too big for the wire size but gives alot of
cushion room since the coils only pull 6 or 7 amps .

It's not a fuse that I want to have blowing out too easily .

The problem with a fuse link is that if a temporary problem causes it
to blow it's much more difficult to replace than a fuse .

Heavy gauge wire is a good idea and 12ga. is more than enough and
will be safe with a 30 amp fuse if you wanted to go that big .

If you want to get fancy order-up a 1mfd. 400 volt capacitor and wire it
between the coil pack hot , near the coil , and ground , this will cut down
on the posibility of spikes getting back into you electrical system .

...................Jim

MegaScott · Post by **MegaScott** » Sat Apr 15, 2006 10:46 am

Wes,

I would use switched power to the coils. If for whatever reason your module goes bad or you get a short in the wiring and continously grounds out the coils you won't burn out your coils or possibly start a fire. The OEM Ford EDIS wiring powers the coils off the Ignition switch, hot in start or run. I would use either pin 37 or 57 of the EEC to power the coils.

You should never run power directly off the battery unless it is something that is designed to have power at all times. On the stuff that is powered directly off the battery it should be fused as close to the battery as possible.

wes kiser · Post by **wes kiser** » Sun Apr 16, 2006 6:01 am

I will likely install a relay underhood then, and let my existing coil and tfi circuit pull in the relay. If the coils really do only pull 6 or 7 amps, then I may just wire the module and coils to the existin ignition circuit. The way that wire was sized lead me to believe ford thought it may want about double that.

For me the relay will be cheap and easy. Does anybody make a connector that will plug in place of the tfi module and allow me to pick up my power, spout (saw now), and pip? I tried cutting up an old tfi and tapping onto the pins, but I am really not happy with the results (settled for just pip and spout, then covered it with hot glue to keep the wired from breaking off).

On a side note, will the idm circuit properly drive my tach in my 4 cylinder 87 mustand, or will I need to make the simple circuit outlined in the instructions? Thanks again for the replies.

Minami Kotaro · Post by **Minami Kotaro** » Sun Apr 16, 2006 1:39 pm

I'm having a little trouble along these lines as well, or I think so, at least.

I'm having problems with 18v coming *from* the module itself on the SAW (wire #3) when the MS is completely disconnected (SAW unplugged from the relay board, MS not even in the car).

I was thinking that, somehow, even though it isn't likely, the 12v wire from either the coil #2 or on #8 was getting crossed with the SAW. I was going to run the coil directly from the battery, thus completely isolating the 12v wire (#8 ) on the module from everything else, to see if that helped anything.

I currently have #8 on the module and #2 on the coils (the middle wire, with the little can) running off the 12v switched wire from the ignition that used to be the old coil's "hot" wire.

wes kiser · Post by **wes kiser** » Sun Apr 23, 2006 5:44 am

Got it running with EDIS. For the record the idm drives a 4 cylinder mustang tach. Since it only needed to be fused at 15 amps, I just used my existing coil circuit for everything.