New coil + Ign module

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Re: New coil + Ign module

Postby Liteace » Thu Feb 14, 2013 10:18 pm

This vehicle has no PCM, its an old 1983 Ford mustang 2.3 pinto, with a carb & conventional ignition system, the duraspark box was taken off as it didnt work and replaced with a brand new GM HEI module, the tach dont work as its not connected, connected when scope screen was grabbed is:

direct +12 feed from battery to ignition module + coil,
coil neg to module

Ive load tested the earth on the module and thats good, the distributor is also new :?:

:?
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Re: New coil + Ign module

Postby Robski » Thu Feb 14, 2013 10:26 pm

Ive load tested the earth on the module and thats good, the distributor is also new


How did you do that ?

Where was you grounded with CHA & why does it go sub zero ?
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Re: New coil + Ign module

Postby Liteace » Thu Feb 14, 2013 10:37 pm

Rob I didnt use scope to check ground I used teslite on bat poss to module heatsink + body\chassis + engine and it was all good :?:
Ch A was gounded on bat neg
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Re: New coil + Ign module

Postby Fat Freddy » Fri Feb 15, 2013 5:55 am

no PCM, its an old 1983 Ford mustang 2.3 pinto, with a carb & conventional ignition system


My apologies. :oops: You did say that at the start. The GM module sent me off.


ie. How is it possible for the coil current to still be 6A after the PCM has removed ground path. I assume this from what is being shown in CHA, after the 1.2ms time to saturate the line rises to 12v again?

I'm not at all familiar with the setup, and have never delved much into the reams of coils with more than a simple power and ground circuit. I'm aware some can be triggered on a 3rd wire, and even have a forth wire for a feedback of succesful spark (thinking about COP here). I realise a DIS on wasted spark would have a common power lead, and 2 switched negatives.

So, coming back to this case, if on CHA the ground return has been removed, why does it not induce a spark? We see that the ground path is completed to charge the coil, then it appears that the PCM drops the path, surely that should induce a flux collapse there and then?


Are you referring to where it has gone into current control? It hasn't completly switched off. I guess it's supplying just enough energy to sustain the magnetic field.


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Re: New coil + Ign module

Postby KimAndersen » Fri Feb 15, 2013 1:09 pm

Hi Liteace

Do you have a oscilloscope image of the pickup from the ignition distributor ? I would be nice to see if the signal are making some disturbances to GM HEI module.

As you can see on this image taken from a High Energy Ignition Circuit MC3334 from Motorola which are used in the GM HEI module - the pickup coil are connected to the amplifier called ( Dwell Reference Buffer ) and that signal are used to charge a capacitor - which in the end calculates the dwell time.

Also a other thing - the ignition coil and the GM HEI module are they purchased as a kit :!:

MOTOROLA_MC3334.jpg


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Re: New coil + Ign module

Postby Liteace » Fri Feb 15, 2013 3:28 pm

Ive got here:

Original motorcraft distributor + coil + non working corroded duraspark module & new aftermarket non working duraspark module
Procomp kit = coil + distributor + module (large red box)

Its a bit of a long story with this vehicle, I'll try and make it short. it got purchased after it had been sitting in a garage for 10+ years, we got the vehicle pulled the engine out, the owner took the rest away to sort the body\paint, we stripped and rebuilt engine with parts supplied by the owner, forged pistons, race cam, dustbin lid size valves + big ends, mains + all the other parts + a edelbrock carburetor that I think is jetted for a 350ci V8 !!!!!!!!!!
When the engine was done the owner took it away, he tried to get the car running using a combination of all the parts he's got & I think maybe he shorted a few things out.
We got the vehicle back as he could not get it running, it had the original motorcraft distributor fitted and all the other parts in the boot. I got the new GM module and wired that up with the procomp coil, got the vehicle running and left it at that for a later date.
The main problem is I can go 2 days to 2 weeks not going to the workshop if I got onsite work to do, the guy who I work with he's a poke and hope, so he's swapped and tried loads of parts to see if he can get it running better, Ive got no time to be peeing about with shite like this + the owner has run out of money.

He's a oscilloscope image of the distributor
https://www.picoauto.com/support/topic9565.html

This distributor is was is now fitted with the GM module and procomp coil. Next on the list when I have time is to test the original Motorcraft distributor, if thats OK I will refit that + good known Ford coil and check again

:)
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Re: New coil + Ign module

Postby KimAndersen » Sun Feb 17, 2013 12:12 pm

Hi Liteace

The oscilloscope image of the distributor pick-up seems a little inconsistent - i would have thought that the amplitude should have the same height.

There may be a issue with the pickup signal polarity - I have read that if one use a GM HEI module must the signal needs to turn on with a positive signal and off with a negative (dwell control).

It looks like your pickup signal are doing the opposite of this - you could try to reverse the wires from the distributor.It is also important to use low resistance ignition coil at 0.5 OHM to get the current limiting circuit to work correctly.

When i look at the primary ignition image over the current flow reaching the limiter at around 5.8 Amps - it's just perfect. The GM HEI module also needs a good heat -sink and a good battery ground reference to work properly.

I must say - it´s a strange looking primary ignition with a the GM HEI module there is drawing current when the dwell periode is off !!!.

This isnt much - that i can contribute with.

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