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post #1 of (permalink) Old 12-02-2002, 09:01 PM
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Coil on backwards, did I fry my module ???

Well, the TR upgrade almost went great. I hooked up the coil backwards and it ran great for a while. Then I let it sit for a while with the key in the run position. Now it won't start. Did I fry the ignition module? I thought my garage did have a slight electrical burning smell when it happened.

I have the stock module, all I changed was cap, rotor, plug wires, and new E-core coil. Any ideas?

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post #2 of (permalink) Old 12-02-2002, 10:29 PM
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Re: Coil on backwards, did I fry my module ???

I'll take a guess that it won't run now? More than likely it's the coil that went poof. At least, that's what I'd try first. Do you still have the can coil the TFI replaced?
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post #3 of (permalink) Old 12-03-2002, 06:34 AM
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Re: Coil on backwards, did I fry my module ???

Hooking the coil primary up backwards shouldn't hurt anything
- the resistance is the same - except the coil's output voltage
will be reduced - and the plug's don't like the reverse voltage,
so they need a little more voltage to fire. You'd possibly
get drivability problems, but it shouldn't fry anything.

But using a coil with about 1/2 the primary resistance that
the module is capable of handling strains, oveheats, the
module. Then you left the key on, really cooking it.
Running the duty cycle on the module is 66%, Engine Off Key
On it's 100%. The output transistors melt.

That E coil is intended to be used with the later DuraSpark II
module, not the early one like the so-called "upgrade"
calls out. Do a search - you'll find that's a frequent complaint.

The later DuraSpark II modules and the TFI modules both have
current limiters in them AND heavier output transistors so
that doesn't happen.

What you did is like using 4 Ohm Speakers on a stereo that's
designed for 8 Ohm speakers - it works, for awhile - then
you get a new stereo when that one smokes.

Try the older coil, if it sparks it was the coil, but most
likely the module's gone south.

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post #4 of (permalink) Old 12-03-2002, 08:52 AM
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Re: Coil on backwards, did I fry my module ???

not to answer a question with a question, but I mjust did the tr-upgrade on my 81 258, I didn't get the coil yet, but what year module do you need re; duraspark-2 for this and can you get the coil from the same vehicle too? I'm sure were both curious about this if he fried his module?
post #5 of (permalink) Old 12-03-2002, 09:32 AM
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Re: Coil on backwards, did I fry my module ???

If you haven't read THIS, it'll fill you in on all the details.

(BTW, the search function STILL WORKS! There's about 9trillion posts covering this mod. [img]images/graemlins/smile.gif[/img] )
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post #6 of (permalink) Old 12-03-2002, 09:33 AM
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Re: Coil on backwards, did I fry my module ???

I think the smell was coming from the coil over heating. I have a CJ5 with the 304 V8. I recently installed a new distributer with Purtronics & a MSD coil because I did the same thing and left ignition on.My module was ok, but because all my ignition parts were old and my coil fried! I replaced it all. The module is designed to saturate the coil at ignition on so that when you turn over the motor the start voltage at the coil breaks and the motor starts immedately.If you let it set with ignition on the coil saturates and starts to heat up.
You may want to check your start voltage at the coil and make sure it's not to high for the coil. My MSD coil required a balist resistor( it was .8ohm) to drop the start voltage a little. Now the resistor gets hot instead of the coil.
Hope this helps !! Jeff
post #7 of (permalink) Old 12-03-2002, 10:00 AM
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Re: Coil on backwards, did I fry my module ???

The original Ford DuraSpark started being used about late '74,
then almost totally used in '75.
It was just an electronic ignition like most everyone else's
at that time. The spark wasn't really much hotter, but it
did get better control over dwell variations due to loose
distributor bushings - a big help in controlling emissions.

GM HEI started at the same time, '75. The GM was a hotter
spark, more voltage, more current, and a longer spark duration.
Their "secret" wasn't really a secret, they no longer used an
ignition resistor, used an E coil, and their output transistors
were stronger.

About '77 or 78 Ford got around the GM patents and came out
with their DuraSpark II. Then they had something just as
good as GM's. Both ignition systems finally had the same
power, voltage, current and duration. This was really needed
since the mixtures were getting leaner every year, it was
much harder to light a good fire in the chamber.

Both used the larger cap because the extra distance between
terminals was needed for dielectric strength - insulation.

The DuraSpark II uses a different module connector, more
square than the DuraSpark I -- similar, but different.
(OK, it wasn't called I until there was a II.)

Whenever you see the larger Ford cap (stock, not conversions)
you'll find the module is the more powerful DuraSpark II.
The wiring is slightly different on those, and they have
another wire to contend with.

The TFI (Thick Film Ignition) came even later - that's the
one with the small flat module mounted directly on the
distributor. The reason they did that was to try to get
around the false triggering problems the Dura I & II
experienced. The Dura's were very sensitive and would
trigger from electrical noises. (GM got around that problem
by having a higher voltage signal from the pickup coil - 8 tips
passing each other to trigger vs 1, so they could use a
less sensitive module.)

The Ford TFI used the E coil.

The resistance on the E coil's primary is roughly 1/2 that
of the round coil used originally on the DuraSpark I.
The round DuraSpark II round coils were somewhere in between.

The DuraSpark II module also has a built-in current limiter
in it - that's why it does not overheat when the key is left on.

DuraSpark I - when you turned the key on current rushed into
the coil and continued flowing at full strength, ready to fire,
but if you didn't start it it continued pushing the current
through the coil. The original coil resistance was high
enough that it didn't harm the module - usually.
But when you use a coil with less primary resistance, the
current is greater, the output transistors have to dissipate
more heat, often too much -- "Pop."

The DuraSpark II has the current limiter - when you initially
turn the key on, current rushes into the coil to charge it
up, but then the limiter lowers the current substantially,
saving the output transistors.
That's actually a side benefit of the current limiter, it's
main purpose is to limit the amount of magnetic field to
the optimum level in the coil. There is something called
over-saturation in a coil, decreasing it's output - you
can pack it too tight with magnetic field.

I've always been under the impression that the Ford
DuraSpark II did NOT use an ignition resistor in series
with the coil, just straight 12 Volts to it. The GM does
not use the resistor.

But - I was looking at a schematic to be able to tell you
the slight difference in wiring between the I and II and my
book shows a resistor. It may be a misprint, need to
check further.

Not being a Ford enthusiast I've always tried to avoid them
- starting with when they came out with their electronic
ignition in '75, then for sure I lost all respect for them
when they went to computers.

Now - using an E coil with a DuraSpark I -- with the original
ignition resistor still in place, will provide a slightly
hotter spark than with the original points ignition or the
Dura I's coil, but not what it could if it was done right.
But - you have that overheating potential.
Best way then, more reliable, is use the round coil designed
to be used with that mudule.

Best way - do the complete conversion, later II module and
all - and if the ignition resistor is different or none,
do it too.
Then you'll have a spark rivaling an HEI.

I'll try to find out about that resistor and let you know.
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post #8 of (permalink) Old 12-03-2002, 10:10 AM
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Re: Coil on backwards, did I fry my module ???

I had the same problem when I did the TR upgrade...and it did fry the ingnition module. I thought it was the coil at first too, but I got a new one and still no spark, it would turn over just no spark from the coil to the plugs. Bought a new ignition module and it started right up.
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post #9 of (permalink) Old 12-03-2002, 12:05 PM
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Re: Coil on backwards, did I fry my module ???

Wow, Thanks for all the help. I forgot to note it is an 83' cj-5 w/ 258 so I guess it has the dura spark II module??? If I have to replace the module, shall a upgrade be in order I suppose? BTW, I did do a search but the problem IS that there are thousands of posts on this topic and it is hard to search throught the results.

RRich, Shoud I ck my voltage at the coil to see if is 12 or less? If it is 12V, can I wire the resistor in line? Or is that something built into the module?

Also, another thing I noticed last night was that I didn't see a capacitor on the + side of the coil wire, isn't there supposed to be one there?
post #10 of (permalink) Old 12-03-2002, 12:54 PM
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Re: Coil on backwards, did I fry my module ???

I remember reading somewhere in one of the post not to long ago that leaving the key in the run position with the engine off will fry the ignition. Try this
There is a post on it from AllLockedUp that might help you.
Hope this helps
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