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Howell + MSD 6A

2K views 7 replies 5 participants last post by  Orlie 
#1 ·
I purchased an 86 CJ7 from my neighbor, it has the Howell kit installed. I have purchased an MSD 6A ignition and after looking at the wiring from the Howell and the MSD I have some questions. The ECM (computer) connector only has one wire (orange) connected to the ECM after the Howell install. I followed the orange wire from the ECM connector which ends at one of the connectors on the ICM (ignition control module), spliced into the orange wire (from the ECM) is the orange wire twisted with the purple wire (purple wire is terminated on one of the ICM connectors) connected to the distributer connector. Looking at the MSD install it looks like once the MSD is installed I no longer need the computer, is this correct? Looking at the wiring I'm surprised the Jeep even ran, I pulled all the wire loom off the Jeep and Howell wiring and found wires that had been spliced twisted together with no solder or insulation. I will post some pics once I get home so there are visual aids.

Thank you

Orlie
 
#2 ·
We seem to be in the same situation. I recently purchased a 1986 CJ7 with the Howell EFI and ordered the MSD 6A to install and I can't find anything conclusive on the internet about how to wire MSD to the ECM. I tried to call MSD and got put on perpetual hold. I figured I could stumble through it. The original module has the drool of death coming out of it and I did not want to put a red china module on it. When I received the MSD 6A and blaster coil it is made in red china. There is a post on this forum by Jeephammer that says you can use the gray tach output wire to trigger the ECM. Others say you need the 8920 tach adaptor to trigger the ECM because the tach output from the MSD is not a strong enough signal. The MSD replaces the stock Duraspark module.
 
#5 ·
I have ordered the tach filter from Howell and will get it installed. After the MSD 6A and Howell tach filter have been installed what purpose does the factory ECM serve, I'm assuming all the signals for spark, fuel and timing come from the Howell ECM. In my OP I mentioned the one remaining wire
that is connected to the factory ECM (Not the Howell ECM) is one orange wire that went or came from the duraspark module (ICM). This orange wire is spliced in with the orange wire that is twisted together with the purple (purple wire terminates in one of the factory ICM wires) wire that is plugged into the distributer. The MSD install directions for the MSD 6A module has use disconnect the original distributer connection, using MSD adapter # 8869 I will plug the output of the MSD 6A module into the distributer totally eliminating the last wire connected to the factory ECM. If I'm thinking about this correctly after installing the MSD 6A it would totally eliminate the factory ECM. Has any other CJ owner been able to eliminate their factory ECM.
 
#4 ·
Thanks for the reply. Since I am going to try to run a stock tach, I ordered the MSD 8920 to trigger it. I was hoping it would work to trigger the ECM. As I understand it, the Howell tach filter is in the wiring loom near the ECM. I will go ahead and get the Howell tach filter to be sure this thing will still run after I get through fixing it.
 
#7 ·
The factory ignition module will be completely surplus. Because you have a 1986 with a CEC computer originally the orange and purple wires are rerouted through it, the computer then advancing and retarding the signal from the distributor. before 1984 the orange and purple wires went from the distributor direct to the ignition module.

The computer and ignition module can now be removed.

The MSD6A is usually wired to the distributor sensor pickup to trigger the MSD6A and then outputs a tach signal to the Howell through a filter to trigger the injection. This is not the only way of doing it, the filter can cost a few bucks.

The Howell computer is close to a GM design, which itself was intended to work with the GM HEI 7 pin ignition modules. This module is possibly a better buy for your install as an ignition module, it is cheap and commonly found in junkyards and part stores and intended to work with fuel injection.

However you can still use the MSD6A for multiple spark discharge at low revs, if that is something you want. The GM HEI 7 pin unit is wired in to the distributor to pickup the signal and outputs a nice square wave form signal to the Howell. It has a seperate output to switch the coil and this coil output can be used to trigger the MSD6A which itself can then fire the coil.

Sounds like a but more work but the 7 pin module is around $30, compared to a list price on the 6A of around $200.
 
#8 ·
The factory ignition module will be completely surplus. Because you have a 1986 with a CEC computer originally the orange and purple wires are rerouted through it, the computer then advancing and retarding the signal from the distributor. before 1984 the orange and purple wires went from the distributor direct to the ignition module.

The computer and ignition module can now be removed.

The MSD6A is usually wired to the distributor sensor pickup to trigger the MSD6A and then outputs a tach signal to the Howell through a filter to trigger the injection. This is not the only way of doing it, the filter can cost a few bucks.

The Howell computer is close to a GM design, which itself was intended to work with the GM HEI 7 pin ignition modules. This module is possibly a better buy for your install as an ignition module, it is cheap and commonly found in junkyards and part stores and intended to work with fuel injection.

However you can still use the MSD6A for multiple spark discharge at low revs, if that is something you want. The GM HEI 7 pin unit is wired in to the distributor to pickup the signal and outputs a nice square wave form signal to the Howell. It has a seperate output to switch the coil and this coil output can be used to trigger the MSD6A which itself can then fire the coil.

Sounds like a but more work but the 7 pin module is around $30, compared to a list price on the 6A of around $200.
This is exactly what I needed to know, it's is hard to determine what exactly the previous owner has done to the wiring and how they installed anything. After I pulled all the wire loom and exposed the wiring I was shock at the mess I saw. There were wires spliced everywhere with no insulation ver the exposed wire.

For the MSD I'm not to worried about the cost, the way I look at at it $200.00 is way better than driving around town looking for GM HEI hardware, as I've gotten older my time is way more valuable. That you you guys for all the great info, hopefully I can help someone else in the future.

Orlie
 
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