2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

trailing coil questions

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Old Aug 3, 2008 | 08:06 PM
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trailing coil questions

Do both coils fire at the same time?

Which wire(s) is(are) the positive dc power for the coil? I'm guessing black and yellow...

Does it ground through the ecu?
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Old Aug 4, 2008 | 05:48 AM
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HAILERS
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No. Trail coils do not fire at the same time.

Black/Yellow is the power.

The ignitors elect componets gnd thru the base of the coil pack contacting the frame. Put the coils on a rubber mat and they won't/can't work.

Read this thread for how the trail and lead coils work: http://www.teamfc3s.org/info/articles/demystifying.html
Attached Thumbnails trailing coil questions-trailignitor.jpg  

Last edited by HAILERS; Aug 4, 2008 at 06:01 AM.
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Old Aug 4, 2008 | 07:26 PM
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ok I read that information,and it was pretty informative.

What I am trying to do here is turn the secondary ignition coil on and off.

Now, can I put a switch in series between the 2 black/yellow wires to turn off the trailing coil.

I am aware that the secondary coil provides rpm signals to the tach and ecu. Currently I am getting that signal from my MSD.

Now can I tie the two power wires together to a single pole single throw switch?

Or will in need a two pole single throw switch?

I see that the ecu sends a 5 volt signal to the coil, but thats not the power wire so i feel like I should be able to go single pole single throw. But then why are there 2 power wires?
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Old Aug 4, 2008 | 08:36 PM
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Originally Posted by ITSWILL
ok I read that information,and it was pretty informative.

What I am trying to do here is turn the secondary ignition coil on and off.

Now, can I put a switch in series between the 2 black/yellow wires to turn off the trailing coil.

I am aware that the secondary coil provides rpm signals to the tach and ecu. Currently I am getting that signal from my MSD.

Now can I tie the two power wires together to a single pole single throw switch?

Or will in need a two pole single throw switch?

I see that the ecu sends a 5 volt signal to the coil, but thats not the power wire so i feel like I should be able to go single pole single throw. But then why are there 2 power wires?

Two power wires because there are ......2 coils.

From the article that was attached::::::::::::::: Focus on the Select signal. Trailing primary #1 fires when the Select signal goes from 0 to 5 volts, while trailing primary #2 fires when the Select signal goes from 5 to 0 volts. So while there is only one IgT signal for both coils, the trailing igniter knows which coil to fire based on the rising or falling edge of the Select signal. Certainly, an interesting and unique approach.

I know zip about coils etc. I'll stop here.

EDIT: Forget what I wrote in this space. What you need to do to stop the Trail coils from firing, is to disable the SELECT signal. Do it with a relay or switch or whatever. Kill the select signal and they won't fire.

SELECT signal is on the BR/Y wire in the four wire connector.

Or kill the TRIGGER signal?

Last edited by HAILERS; Aug 4, 2008 at 09:06 PM.
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Old Aug 4, 2008 | 09:10 PM
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Or kill the feedback signal. No feedback signal, no firing.
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Old Aug 4, 2008 | 09:45 PM
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Thanks for the help.

Wait why would the feedback signal stop it from firing? It just sends the rpm signal to the ecu for fuel mapping... right?

I think the select signal makes the most sense.

Last edited by ITSWILL; Aug 4, 2008 at 10:04 PM.
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Old Aug 5, 2008 | 08:57 AM
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Yeah. Feedback signal on 1X was a ................mistake.

Anyway, to prove the other two, just depin one at a time and I'm sure the Trail coil assy will not fire on either of its coils. Depin them at the ECU.
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Old Aug 6, 2008 | 12:16 AM
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I'll give it a shot this weekend and let you know how it worked.
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Old Aug 10, 2008 | 11:48 AM
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Didn't work???

Any suggestions?

Also I am supplying the feedback signal and the tach signal with my MSD.
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Old Aug 10, 2008 | 02:59 PM
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What part did not work? Your Trail coils still work with the Brown/Yellow wire disconnected/interrupted? The Select signal?

MSD is sending signals to the ECU????

I think I'll drop out of this thread. I know not of MSD, but did notice on this day, this hour, a thread that dealt with MSD's. You might open another thread and I'll stay out of it.

Last edited by HAILERS; Aug 10, 2008 at 03:06 PM.
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Old Aug 10, 2008 | 09:15 PM
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well if i turn off the trailing coil the ecu will not get the rpm signal to the ecu so i just used the rpm signal from the MSD.

Thanks for your time.
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