Ignition Control and MegaSquirt

Q. What ignition options are there for MegaSquirt?

A. If you need electronic ignition control as well as fuel control (i.e. you can't, or don't want to, run a 'standard' distributor), you have a few options.

One option is the MegaSquirt-II daughtercard for MegaSquirt® controllers that will run the GM 7-pin HEI, GM DIS, and Ford EDIS, as well as some others yet to be determined. It also has dual 1212 VE and AFR tables, as well as an independent 1212 spark advance table and stepper motor IAC control. You can find out more at the MegaSquirt-II site and ask questions at the MegaSquirt-II forum.

There are other, older possibilities out there, like MegaSpark, but these are less well supported.

Q. Does anyone have information on the Ford EDIS modules?

A. Here is some info on EDIS modules for 4cylinder applications:

The parts below are for a 1993, 48 States, 1.9 Liter, manual transmission, Ford Escort - unless otherwise noted:

EDIS Module
F1CZ-12K072-A - ford part number
Motorcraft DY-630 - aftermarket part number

You can get your EDIS stuff from a mid '90s Escort with the 1.9 SPFI engine (SOHC with tubular aluminum intake manifold). Get the 36-1 crank wheel off the motor, the sensor, and the coil pack w/mounting bracket. And try to get as much of the harness as you can.

If you're at a pick and pull, look for a motor lying around - it is easier to get the pulley with the motor out of the car - and people seem to pull them to get the transmission. The pulley and sensor can be seen through the left side wheel well, there may not be enough room to get it out with the motor in the car. The complete pile has been purchased for as little as $24 (complete with racy red plug wires!).

The EDIS module is hiding behind the engine compartment fuse block. The crank wheel looks like a powdered metal ring on a steel center with the belt pulley in "front" attached by a rubber layer. The whole thing looks like one piece but it's not. The ring of teeth is just pressed onto the center section which has the pulley attached by rubber. The 144mm OD trigger ring is a press fit on the hub, so it can be adapted to just about anything that the 103mm ID of the ring will fit onto. The ring is 7mm thick where it presses onto the crank hub. The teeth are 2mm thicker, 4mm wide, and 8mm deep. To remove the ring, all you have to do is put the wheel in a vise face down. Put it in so that just the teeth are touching the vise on either side. You can heat it up a little and then with a hammer hit the center. With a few whacks the center falls out and you are left with a nice thin ring of teeth.

It appears that Ford used different mounting techniques for different for 6 cylinder vehicles. The "attached by a rubber layer" doesn't apply to the 6 cylinder EDIS from a 1985 Windstar 3.8 liter. The wheel is attached via four bolts and has the following dimensions:

OD 4.72 "
ID 2.83 "
thickness 0.35" at OD
thickness 0.12" at ID

(the transition between these two thicknesses occurs at a diameter of 3.8 " There are 4 bolt holes in a 90 degree arrangement hole diameter 0.23 ". hole centerline separation 3.16 ")

Except for the V-10 with a 40-1 trigger wheel, apparently all of the EDIS systems used a 36-1 wheel. You can use a 4 cylinder Escort wheel or a V-6 wheel.

For anyone looking for the EDIS-8 module, it can be found as a replacement ignition module from companies such as Autozone. For instance, ask for the ignition module from a '93 Lincoln Town Car and it will cross to a WELLS # F143. The WELLS part says Motorcraft on it and looks to be the exact same part. Price is about $140 compared to FORD's price of $300+.

More information on the Ford EDIS modules can be found at:



Q. What combinations of cylinders/firing can the EDIS modules conceivably be used on?

A. The components of the EDIS system are the crank wheel and the module. The module expects to see a gap every 35 teeth. So let's see what combinations we can get:

EDIS-4: fire every 180 degrees crank
4 cylinder wasted spark (36-1)
2 cylinder direct fire (36-1)

EDIS-6: fire every 120 degrees crank
6 cylinder (even-fire) wasted spark (36-1)
3 cylinder direct fire (36-1)
12 cylinder wasted spark (36-1 with 2 pickups and 2 modules 180degrees apart)

EDIS-8: fire every 90 degrees crank
8 cylinder wasted spark (36-1)
16 cylinder wasted spark (36-1 with 2 pickups and 2 modules 180degrees apart)

Q. What is ion sensing I keep hearing about?

A. Ion sensing can be used for for PPP (peak pressure point) control. For more information see "Spark-Advance Control by Ion-Sensing and Interpretation" at:


Q. I've lost my tach signal to my MegaSquirt! Any ideas?

A. First, hook the board to the stimulator to verify that everything is working in the MegaSquirt box. If it is, then you know the problem lies in the wiring or ignition interface. So check wiring on the car. If the stimulator doesn't 'fire' the MegaSquirt, first check to see that it has a fresh battery [or hook it to a 12V power supply]. If the MegaSquirt still won't detect the ignition signal, you'll need to do some detective work inside the box.

One thing you can try as a test is to use a spare LED with a 330 ohm resistor in series.

Ground the cathode end (flat on LED), put the resistor on the other LED lead, and use the other end of the resistor as a probe. First, probe this to the +12V and verify that it lights. Then, move it from the DB37 connector for the tach input, then the John Zener diode, etc - with the stimulator hooked up you should see it blink. By moving the 'test resistor' around, you should be able to isolate the component causing the problem.

One point here for everybody: as a *normal* course of getting the MegaSquirt system running the first time, Bruce does not recommend re-installing the embedded code - only as a last resort. The processors shipped with the V1 boards were all verified to work. When you do an install for the first time, be sure to check everything else first, like connector, power, drivers, tach, etc. - 90% of the problems will be in these - especially if you get proper operation on the stimulator.

And, be sure to change only ONE THING AT A TIME, and test after each change. Do not change several things all at once - this will get you in trouble for sure.

Q. I don't seem to be able to get a 'clean' tach signal. What can I do?

A. Usually, you can just hook the MegaSquirt® tach signal wire to the tach pin on your ignition and it will work fine. For some installations, however, getting a decent tach signal may require some trial and error.

If you do have problems, though, see the ignition triggering advice here:


MegaSquirt® and MicroSquirt® controllers are experimental devices intended for educational purposes.
MegaSquirt® and MicroSquirt® controllers are not for sale or use on pollution controlled vehicles. Check the laws that apply in your locality to determine if using a MegaSquirt® or MicroSquirt® controller is legal for your application.
©2004, 2005 Bruce Bowling and Al Grippo. All rights reserved. MegaSquirt® and MicroSquirt® are registered trademarks. This document is solely for the support of MegaSquirt® boards from Bowling and Grippo.