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HEI Ignition Module Modification/Installation

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First off, thanks to Joe Bialy over on ProbeTalk for the original idea and write up. A great idea with a practical purpose :biggrin:

NOTE: All pictures shown are hosted from the uploads site. However, if you need a larger/higher resolution picture, they are hosted on the links above or below the picture. If someone wants to offer redundant file hosting (my site goes down periodically, and is bandwidth limited) that would be great.


This modification is intended to remedy a common problem that occurs on many '93/'94 (and '92 in AUS) V6 Mazda 626/MX-6/MX-3/Millenia ignition systems. The distributor on these cars has both the coilpack and igniter module built-in, which while a space-saving design, is prone to heat-related failure (the distributor bolts straight to the head of the motor). Specifically, a transistor within the igniter module fails (either permanently or intermittently) causing weak/no ignition spark. Symptoms range from rough idle, poor performance, struggling to achieve higher RPM's, and even intermittent loss of engine power. In extreme cases, the car will not start at all, or will restart once the motor has cooled down. The problem only gets worse. Also contained within the distributor are two hall effect sensors; one is used to determine the crankshaft position, the other, camshaft position.

One solution to the problem is to use a larger, cheap, reliable igniter--the HEI module used on many 70's and 80's era GM vehicles, including their well-known 350 V8. This module can handle firing 8 cylinders up to at least 7,000 rpm, so it should be able to keep pace on our V6 to at least 9,300 rpm (well above the rev limiter). The part costs $13 at Advance Auto Parts (mfr. is GP Sorensen, part number EL102; other brands will work fine).

Here is a picture of the igniter module and hall sensors (i.e. camshaft and crank position) (it's pretty small, about 3/4" in length). The igniter module is the square-looking thing with 5 pins (only 3 are used), and is mounted flush in the bracket. The other two modules are the hall sensors.



Here is an image of all of the distributor parts, disassembled. To take it apart, you just remove all of the screws and pull it apart in layers. The screws are on very tight (lock washers) and a vise and large flat-tip screwdriver are very helpful.



Additional Notes

This modification can be adapted to work for the '95 and later models as well, however since I did not perform the modification on any other than the '93/'94, the only suggestion I have for you if this applies is to compare the wiring diagrams given in the Joe Bialy write-up. Several users on ProbeTalk have gotten this to work on their '95 models.

Tools and Supplies Needed

  • 8 mm ratchet (to remove distributor cap)
  • 12 mm ratchet (to remove distributor)
  • Vise/clamp to hold distributor while you loosen screws
  • Large phillips and flat-tip screwdriver
  • #2 Phillips Screwdriver
  • Soldering Iron
  • Solder
  • Spade Terminals (1 small, several large)
  • Ring terminal (small)
  • GP Sorensen EL102 (or equivalent) HEI module (many other HEI modules will work fine)


Joe Bialy's write-up is available at this link:


Another useful and helpful site:


I performed the same result, but without hacking up the wiring harness as these folks did. Instead, since I had a spare distributor, I made the modifications to the wiring inside the distributor. This has two advantages--I can revert to the factory configuration (since the factory harness is uncut) by simply swapping in a factory distributor (or soldering the factory igniter back inside and removing the 3 wires); it also provides less risk to your car (i.e. many people do this mod before replacing the distributor...well after you cut the factory harness, and this doesn't work, you have to revert to the factory configuration and put in a new distributor anyway) and is again, easier to reverse.


  • Disassemble the distributor. Start by removing the cap and rotor, and then the screw to the condenser/capacitor on the housing.
  • Next remove the rotor shaft screw, and the 4 screws holding the dust cover and coilpack down.
  • Disconnect the metal band going from the middle pin of the 3-harness plug to a small screw (NOTE: It's not really the "middle pin" it just looks like it is)
  • Gently pull out all of the "guts"
  • Pry/bend/cut out the igniter, making sure to leave plenty of room to solder on the pin closest to the outside of the distributor.
  • Solder a ~2 foot length of wire onto the outside pin that was previously connected to the igniter. This goes to the "Blue/Orange" wire referred to in Joe Bialy's original write-up, and is internally connected to the far-left pin of the (distributor side) connector. You will onnect the other end of the wire (with spade terminals and solder) to pin "G" of the HEI module.
  • Solder another wire to the middle female spade terminal of the 3-pin connector (it's the one with the metal strap). This wire is the "Yellow/Green" wire in Joe Bialy's original write up. It will connect to pin "C" of the HEI module, and is internally connected to the far right pin of the 3-pin harness (distributor side).
  • There are two more female spade terminals left on the 3-pin harness. Solder a wire to the one that is spaced furthest from the other two. Looking at it from the harness/connector side outside the distributor, it's the one on the far left. This is the "Black/Pink" wire in Joe Bialy's original writeup, and will connect to pin "B" of the HEI module.
  • Route the wires in such a way to avoid getting them pinched by the assembly when reassembled. To do this I had to melt a tiny hole in the edge of both the dust cover and distributor cap. Also, make sure you avoid running the wires too close to the ignition coil or you may pick up noise.
  • In addition to melting/cutting a small space for the wires to feed through, you need to cut off the two small tabs on the dust cover that separated the 3 spade terminals on the 3-prong connector. This is because the wires and solder are too thick for it to fit in between. Make sure of course that the wires and prongs are not bent/touching each other (bend them apart as necessary).
  • Wrap the 3 wires together with electrical tape, leaving a region so that you can feed them through the distributor cap.
  • Reassemble the distributor, being careful not to pinch the wires. Make sure the assembly spins freely without obstruction.
  • Mount the HEI module to a SOLID GROUNDING POINT. The module has 4 pins, but it gets its grounding through one of the mounting bolt holes. It will flow between 5 and 10 amps of current, so it needs a solid ground. Also, ground pin "W" (small wire is ok for pin "W").

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Here are some more pictures/diagrams to help you along:

This is the pin you must solder a wire to, and connect to pin "G" of the HEI module. You must first completely remove the igniter module (either cut, bend/snap the connections, or desolder...desolder failed for me, as you need a high-power soldering station since the mfr. used high-temp solder).


This shows all 3 wires soldered, with the hall sensor wheels installed.



Modified distributor cap:



Close up of wires coming through distributor cap:



Shot of final assembly:



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All of the pictures (and a few more) are viewable here:


Keep in mind these are very large files (4 megapixels) so don't download anything unless you need it or you will eat up my bandwidth and I'll be forced to shut the file site down temporarily, leaving users who need this info without it.

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You can also connect an external ignition coil (first remove the internal one). This wiring diagram is correct for both setups (with and without external coil), except of course if you want to use the stock coil simly don't hook up the two wires for the external coil:

(Image courtesy of incony.org)




The wire colors may not match your distributor, but the pin locations are correct for the '93/'94 models (as described in the Procedure).

You also need to add a prong to your distributor cap if you want to run the external coil, and connect it to the coil with an ignition wire. Alternatively, you can use a KL-ZE distributor cap (or a KF-ZE), as these cars came with external coils on essentially the same distributor from the factory.

Here's a backup link of the same file:


Here is an alternative (same information) represenation of the same diagram (thanks Omaha95PGT and Joe Bialy, from ProbeTalk):




Backup link:


If you found this information helpful, help to keep the site running by donating! Visit http://mazda626.servehttp.com:8080 for more information on this and other projects, as well as information on how to support the fileserver site!


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