View Full Version : GM Ignition System

08-19-2010, 09:50 AM
Going back to the early part of this century, somebody figured out how to use a GM ignition module and GM coil to replace the Toyota coil and ignitor setup. I am unsure of who to attribute credit to for this - but I'm pretty sure it was a young, broke and innovative mini-truck guy with a carburated 22R. Last year I made the switch from points to electronic ignition and I've always wondered what I would do when the Toyota ignitor finally gave out. Searching the junk yard as often as I do, I seem to get there too late for the dizzy, coil/ignitor and locking hubs:(. These are the first parts that get pulled by the regular people pulling parts in the junk yards. The current retail price for the Toyota ignitor is $636 from the dealer.

A bit of background on why this project came up...

The cam shaft in the Mule has been worn out since Randy got the truck. The worn cam shaft did not affect the Mule's trail ability but on the open road it did not have any umph on the top end. When he rebuilt the 2F engine (still on the stand in his garage) Randy set asside the camshaft and lifters to someday be put into the Mule. Last week that day arrived and the swap was done. Upon getting everything buttoned up, there was still no umph on the top end. After further investigation, Randy found the advance in his distributor was broken. He pulled his distributor and sent it out for service.

Having just completed the cam shaft swap in the Blue Mule, we both wanted to see how it would run. So we set about to put a Toyota ignition system in the Mule. Randy was able to source an electronic distributor but we were missing the ignitor and coil. I had always wanted to try GM ignition and now seemed like the appropriate time. The GM system is in my truck and my Toyota parts are in the Mule. Oh yeah, the Mule is running much better on the top end with the swapped cam shaft.

Back to the GM Ignition System tech...

This system will replace the Toyota coil and ignitor setup on carburated electronic ignitions. If you are fuel injected or points - this will not work for you. For Land Cruisers, it will work with the 1978, 1979 40 series small cap and 60 series big cap electronic distributors. I'm not as familiar with mini trucks and when they started using electronic (versus points) distributors. While it is pretty straight forward, you need to pay attention to the details.

There are 3 threads out on the net that cover the details of this system.
MUD Thread (http://forum.ih8mud.com/40-55-series-tech/266672-ignitor-schematic.html)
Pirate Thread (http://pirate4x4.com/forum/showthread.php?t=179253&highlight=bypass+ignitor)
zuwharrie thread (http://bbs.zuwharrie.com/content/topic,85514.0.html)

The price of the parts has gone up from what you see in the threads above - but still less than the Toyota OEM ignitor; the ignition module is $25 and the coil is $18. Here are the boxes and part numbers from NAPA. These are common parts and you can walk into the parts store and get a coil for a 1972 Chevrolet k10 4wd truck with a 350 CI engine and get an ignition module for a 1979 GM truck with a 350 CI. In addition to the parts, you should have some wiring an connectors to hook everything up.


When mounting the ignition module, it needs to be mounted on a metal base and both mounting holes need to be used. The module is all plastic on one side and has a metal strip on the other. The module needs to be mounted plastic side up, metal side down. Mounting the ignition module in this manner insures there is continuity between the mounting holes - this continuity is required for the system to work.

For the installation I'm running, Randy fabricated a metal base for mounting the ignition module, the metal base attaches to the coil bracket. This is very similar to the Toyota configuration, where the coil sits in the bracket and the ignitor is mounted to the top of the backet.

A clean and strong connection to (-) ground is required. In my installation, the coil bracket has a connection directly to the the negative battery post. Make sure you have a good ground connection - if you don't have this, the system will not work. DAMHIK :o

The wire connections coming off the ignition module are very straight forward. The module has four connection points and they are labled; B, C, W and G.

W and G connections
The W and G tabs will connect to the two wires that come out of the Distributor body. These are the pickup wires. On the electronic Toyota distributors one of the wires is white and the other is pink-ish-red. The pickup wires from the distributor terminate in a green plug from the factory. For the installation that I am running, I spliced in a green plug (from the junk yard) to my W and G wires so I am able to use the factory plug on the distributor. The W tab connects with the white wire and the G tab connects with the pink-ish-red wire.

B and C connections
The B and C tabs will connect to the coil posts. The B tab connects with the positive (+) post of the coil and the C tab connects with the negative (-) post of the coil.

The ignition system needs to get 12 volt power when the engine is running. If you are replacing an working ignition system, use the "key on power" wire (typically black with yellow stripe) and attach it to the (+) post of the coil.

Oh yeah, the coil wire needs to go from the coil to the center of the distributor.

Mount the ignitor to metal, connect the metal to a good ground.
W = white wire from the distributor
G = pink-ish-red wire from the distributor
C = negative side (-) of the coil
B = positive side (+) of the coil
"Key on power" to the positive post of the coil

I will clean up the wiring and connections and continue to run this system in my rig. I'll carry my Toyota coil and ignitor as a backup; as I am curious to see how this system holds up over time. Like most of my projects, it was an educational experience - Randy thanks for your help in getting this project done. I've been running it since Sunday and am pleased with the way it works. I noticed an immediate improvement in peformance, but it could be because of a timing adjustment (2 degrees) that I made at the same time. Here is a photo of the system in my truck.

08-19-2010, 04:38 PM
Wow...I'm going to have to "bookmark" this :thumb:

08-20-2010, 01:28 PM
Interesting. I have a 1978 Distributor (still in the long block) on one of the engines I have on a stand in my garage. I haven't done anything with it because I don't have the coil and ignitor to go with, but it looks like I could use this approach instead, right?

But I have always H8Ted the idea of using chebbie parts in my Land Cruisers :eek:

08-20-2010, 01:37 PM
Interesting. I have a 1978 Distributor (still in the long block) on one of the engines I have on a stand in my garage. I haven't done anything with it because I don't have the coil and ignitor to go with, but it looks like I could use this approach instead, right?

But I have always H8Ted the idea of using chebbie parts in my Land Cruisers :eek:

Yes, this ignition set up will work with the 1978 distributor.

I understand the desire to use Toyota parts, but there is nothing wrong with having options:D.

06-08-2017, 04:34 PM
Thanks man for this write up. Your legend lives on :D

FWIW, the OEM FJ60 Igniters are now unobtanium... used parts on SOR and similar are north of $350 for a used unit. This has become a solid option for me. Thanks Ricardo.