Coil Polarity Changed, Added 5 Mpg - Mercedes-Benz Forum

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post #1 of 11 (permalink) Old 08-20-2004, 07:20 PM Thread Starter
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Coil Polarity Changed, Added 5 Mpg

I connected the coil positive terminal to ground, and connected the coil negative terminal to the ignition module.
In other words, I connected the positve terminal of the coil to the chassis (ground).
Then I connected the negative terminal of the coil to the ballast resistor.

Gas mileage went up 5 mpg to 17mpg, the exhaust tone became resonant, clear and crisp, and no more gas smell was coming from the tailpipes.

Go to Page 96, Section 10, Haynes manual for 1968-1972 230, 250 and 280 and read this statement:
If the negative terminal of the coil is connected to ground, expect up to a 60% LOSS of spark plug energy.

I know this is counter-intuitive, but the results were amazing. Anyone else been there, done that? [?]
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post #2 of 11 (permalink) Old 08-24-2004, 06:21 AM
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RE: Coil Polarity Changed, Added 5 Mpg

if you connect the coil backwards, the spark travels the wrong way through the spark plug, causing a weak spark, esp at higher temps.

I had this issue on a 1963 MG which had positive earth... I imagine your car is also +ve earth, hence + connection on coil needs to go to ground
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post #3 of 11 (permalink) Old 08-24-2004, 09:57 AM
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RE: Coil Polarity Changed, Added 5 Mpg

[:D]+/-//-/+ battery mate if it neg earth then it wont work, the coil principal is low and high tention, putting a high tention down a low tention would blow the crap out of it
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post #4 of 11 (permalink) Old 06-01-2014, 11:47 AM
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I know this is a very old thread, but I was wondering if anyone had anything else to add to this.
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post #5 of 11 (permalink) Old 06-01-2014, 06:15 PM
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I dont believe it. The coil is a step up transformer - taking a 12 volt spike up to 20,000 (or more in some cases) spike. Hooking it up backwards would take a 12 volt spike and reduce it by a factor of equal value.

Last edited by Grubeguy; 06-02-2014 at 06:43 PM.
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post #6 of 11 (permalink) Old 06-02-2014, 06:30 PM
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non sense . there is a reason why the coil has a marked polarity
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post #7 of 11 (permalink) Old 06-03-2014, 04:58 AM
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An internet search for "ignition coil polarity" quickly reveals more information on this subject than anyone wants to read. Here, for example, is one article that explains the polarity issue fairly well: Ignition coil polarity
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post #8 of 11 (permalink) Old 06-03-2014, 09:21 AM
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If it says so in the Haynes, then it must be suspect.
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post #9 of 11 (permalink) Old 06-03-2014, 03:20 PM
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Quote:
Originally Posted by ejboyd5 View Post
Here is one article that explains the polarity issue fairly well: Ignition coil polarity
I'm big enough to admit when I'm wrong (and I should have known better up front) - the coil + and - posts complete the circuit for one set of windings, where the main wire completes the other, higher voltage circuit. I'm not convinced reversing the things would give better mileage and a smoother engine, but it wouldn't necessarily kill the car...
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post #10 of 11 (permalink) Old 06-04-2014, 07:18 AM
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I wonder if this works for some folks who have bad coils in the first place. If you measure the resistance from 4-1 and 4-15 and it isn't all that different, then maybe it's ok to swap 1 and 15. All kinds of funny stuff is done to get coils to produce more spark than they can when they are crapped out. The OP probably went looking for a better solution because the OEM configuration wasn't working correctly for some reason. If your spark is good in oem configuration, then there's no need to mess with it. Plus, it's easier to diagnose the bad component because you have other oem examples to compare / swap parts with and even written specs. Once you are off the ranch, you are own your own.

There's my $0.02.




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