How to: GM Duraspark ignitions in parallel for TBI - Page 3 - Off-Road Forums & Discussion Groups
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post #21 of (permalink) Old 01-18-2004, 09:13 AM
brendan
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Re: Anyone install an MSD on their Howell TBI??

I don't know about the DS module, but the orange and purple can be swapped around to either pin. It just throws the timing off by a tooth on the reluctor.
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post #22 of (permalink) Old 01-18-2004, 09:19 AM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

What do you mean ORG and PPL can be swapped to either pin? Which pins? Can you explain how it affects the spark timing?

Thanks,
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post #23 of (permalink) Old 01-18-2004, 09:59 AM
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Re: Anyone install an MSD on their Howell TBI??

Hi Tom,

Here is some info from customefis.com that I saved before it was taken down. This is where I got the idea to do what you are doing - using a second ignition module to provide the reference pulse. In my case, I have a 4-pin HEI module in the dist and am using a 7-pin HEI module in parallel to send the ref pulse. I am hoping that once the fuel side is tuned, I'll be able to install the 7-pin module into the dist (again using instructions from the old customefis.com site) and control timing using a custom chip. I am in the last stages of putting my system together so I can't say whether it works for me or not. Anyway, here is the info, I hope it helps:

"The second method is to use two ignition modules and wire the magnetic pickup in parallel into both modules. The computer controlled module then only connects to the ECM to provide a reference pulse and nothing else. The stock ignition module is left intact and continues to fire the coil normally. This method could be a viable way to keep the stock timing curves so that you can work on the fuel only control before attempting to work on the spark timing. I use this method often when trying to diagnose if the ECM is controlling timing correctly."

And

"Connect the magnetic pickup wires to the P and N terminals on the GM ignition module. For the Ford Duraspark, the purple wire goes on the P terminal and the orange wire goes on the N terminal. The polarity is important and the only way I know to tell which way to hook one up is to try and check the timing with the GM module firing the coil. "

Robert
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post #24 of (permalink) Old 01-18-2004, 11:56 AM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

Hey Robert,

I have that same info. I actually have the manual from customefis.com and I have been e-mailing back and forth with John. Using the purple and orange wires didn't work. I am going to try all of the possible combinations again before I do my permanent wiring, but the way I have it in the diagram works. If there are any better ways or other ways that it will work, I will update the diagram.

Thanks,
Tom
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post #25 of (permalink) Old 01-18-2004, 12:01 PM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

Robert,

What color are the wires from your dist? and are you in parallel, or series like me?

Thanks,
Tom
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post #26 of (permalink) Old 01-18-2004, 01:54 PM
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Re: Anyone install an MSD on their Howell TBI??

I left out a few key words in that last post.

The orange and purple can be swapped around to either pin ON THE HEI module. I've seen a couple people say on BB's "it's all hooked up but won't fire" and the solution was to swap the org and ppl around on the P and N pins on the 8 pin module. It wouldn't run I'm guessing because

They had tried to set initial timing either before the swap, or just coarsely by eyeballing the rotor onto the #1 post on the cap. The wires being on the wrong pins threw the timing off by a tooth on the reluctor.

Bill USN-1 saves the day here:

http://www.justinternationals.org/Bi...p;threadid=592




post #27 of (permalink) Old 01-18-2004, 02:06 PM
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Re: Anyone install an MSD on their Howell TBI??

Tom,
Since I have a GM HEI dist in my 258 the wires are the stock colors - green to "P" and white to "N". I have both modules hooked up in parallel, so they should both see the same signal. I am a little surprised that your set up wouldn't work in parallel. Just for clarity, the female spade connectors on the P and N terminals on the dist module have two wires coming off of them - one goes to the magnetic pickup, and the other goes to the 7-pin module mounted on the firewall. I would have thought that doing the same with the the pickup wires on the DS dist would have accomplished the same thing.
I'll try to keep all this in mind if I find that my ECM isn't getting a signal when I go to start it later this week. Thanks for all the info.

Robert
post #28 of (permalink) Old 01-19-2004, 01:29 PM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

Speedbuggy:

Can you edit your post and remove the diagrams? I need to change the diagram because I found that the ignition modules will run in parallel. I will post an updated diagram.

Thanks,
Tom
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post #29 of (permalink) Old 01-19-2004, 01:52 PM Thread Starter
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Re: Anyone install an MSD on their Howell TBI??

Here is the updated diagram for running the GM and Duraspark ignitions in parallel. This will allow you to maintain your current ignition system, but add a GM ECM to control fuel delivery.



Later,
Tom
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post #30 of (permalink) Old 01-20-2004, 06:03 AM
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Re: Anyone install an MSD on their Howell TBI??

Tom, I don't think you need the resistor in there for the HEI module.
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