Coil Reversal -- Please Help!!

turtle1173

Chief Petty Officer
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Nov 29, 2001
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437
Hi all,<br /><br /> Many of you have helped me with my problems on a 1976 55HP Chrysler. I have been struggling with this thing for a year now. My problem initially was a lot of missing from the bottom cylinder. It got worse and worse and now I can't get the bottom cylinder to "catch" and it will only hit on one cylinder.<br /><br /> I was just looking through the wiring diagrams in my manual and I might have made a discovery that could make a difference with this.<br /><br /> My coils are hooked up backwards. According to the diagram, the blue wire hooks to "+" and the white or brown wire goes to "-" terminals. Mine are reversed (blue is on negative, white is on positive).<br /><br /> Should the engine even run with it hooked up this way (Obviously it does, although poorly)? Technically speaking, what happens when the engine is run this way? I'm guessing it is terrible on the entire ignition system, especially the coils.<br /><br /> And finally, could this be my problem that I've had for the past year?????<br /><br />Thanks,<br /><br />Shane
 

SlowlySinking

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Oct 31, 2002
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Re: Coil Reversal -- Please Help!!

turtle1173, the engine will run but as you found out rather poorly and with generally poor starting, what happens is that with the spark coil reverse wired the high voltage goes through the block and then arcs across the spark plug and back to the coil instead of through the plug wires to the spark plugs and to the cylinder head and back to the coil, many times the spark also arcs across other engine parts, this reduces the available voltage to the plugs and you get the problems you describe. Connect them correctly and you should see quite a difference. :)
 

turtle1173

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Nov 29, 2001
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Re: Coil Reversal -- Please Help!!

Hi,<br /><br /> My manual talks about something regarding coils as possible to hook them up with "reverse polarity." Is this what is being referred too (hooking them up backwards)? If so it states that it takes 30-40% more voltage for them to do their work and eventually they will give out.<br /><br /> Might this be why my situation has been getting worse and worse because I've been burning out the coils?<br /><br /> I'm anxious to get outside and try this thing out now. Unfortunately it is raining here this morning. Perhaps this afternoon will be better.<br /><br />Thanks,<br /><br />Shane
 

SlowlySinking

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Re: Coil Reversal -- Please Help!!

turtle1173, sounds like your manual is right on the money, reverse the connections (polarity) and you should see easier starting, running, and long coil life. I wonder why it rains just when you want to work on the boat?? Go figure, :mad: <br /><br />,,,,,,,,good luck.
 

turtle1173

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437
Re: Coil Reversal -- Please Help!!

Hi,<br /><br /> Well, more disappointment!!! That seems to be the story of my life with this motor.<br /><br /> I took both coils off today and decided to try a little test I read about on this forum. The test was to put a 1 1/2 volt battery up to the terminals of the coil and see if the spark plug sparks. I don't know if this is a very good test or not. I decided to use a 9 volt instead.<br /><br /> Anyway, when I hooked it up to the first coil, I was getting shocked just from holding the coil. Eventually I found that when I hooked the battery up, if I touched the spark plug, I would get shocked but the plug would spark also. I'm sure it had something to do with being grounded.<br /><br /> The other coil didn't shock me other than when I touchd the plug it would shock me and spark the plug.<br /><br /> When I got done I thought that this was a dumb test because I had no idea what this meant (or maybe it's just me).<br /><br /> So I decided the real test is to just hook it back up to the motor. I put the coil that I suspicioned to be the worst one (first one tested) on the top cylinder. The top cylinder is the one that runs. The supposed good coil I put on the bottom.<br /><br /> Anyway, to make a long story even longer, I started the motor in my boat trash can and it was still hitting only on the top cylinder. I pulled the bottom lead of the plug and there was no change. I pulled the top plug wire after putting the bottom one back and it just died.<br /><br /> I haven't switched the coils again to see if it changes cylinders. I did that a few months back and it didn't make a difference. I really thought hooking up the coils correctly this time (the wiring) would make the difference but it is the same story. I guess that's the last straw with this engine.<br /><br /> Sorry for such a long post.<br /><br />Shane
 

SlowlySinking

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Re: Coil Reversal -- Please Help!!

Hi Shane. by switching the coils and still having the same plug not fire indicates that both coils are okay, I would suspect the wiring, connectors, etc that feed the bad cylinder. Try this, disconnect all wires from both coils and using an OHM meter check the resistance between the wires that feed one coil and then the same wires that feed the other coil, then do the same thing from each wire to the engine block, compare the readings and see what you get. Since you have a manual for this engine, it should detail how to step by step troubleshoot an engine electrical problem. Back to you,,,,,
 

Hooty

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Oct 2, 2001
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4,496
Re: Coil Reversal -- Please Help!!

I'm a little confused about the "reverse polarity" thing. I assume you're talking about the + & - wires to the primary windings of the coil. What difference does it make? It's just windings around a iron core. Hook your VOM to the wires and read the resistance. Then switch the leads from your VOM and see if the resistance changes. I'll bet it doesn't. <br /><br />c/6<br /><br />Hooty
 

petryshyn

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Oct 3, 2001
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2,851
Re: Coil Reversal -- Please Help!!

Hooty<br />Turtle is right on this one......if the coil primary is connected in reverse, the secondary polarity changes as well. The required voltage to jump the plug gap increases 30-40%. The reason has to do with the temperature of the center electrode verses the ground electrode. Electrons prefer to go from a hot to a cold, not vice versa. :)
 

Hooty

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Re: Coil Reversal -- Please Help!!

Ahaaa.<br />That makes sense. I didn't think about it changing the secondary polarity. Thanks!<br /><br />c/6<br /><br />Hooty
 

turtle1173

Chief Petty Officer
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Nov 29, 2001
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437
Re: Coil Reversal -- Please Help!!

Slowlysinking,<br /><br /> I'm not very good at electronics (hey, got to learn sometime right?) so let me make sure I have this right.<br /><br /> On my meter, there are 3 settings: x1K, x100, & x10. Which setting should I use?<br /><br /> OK, I would connect the red meter lead to the blue wire (the positive wire) and the black to the white wire (the negative)? Is that right? Then the same thing for the other set of wires?<br /><br /> Then connect the red lead wire to each individual wire and the black lead to the engine block? Is that correct?<br /><br /> Just trying to clarify. My manual seems real vague when I start looking through the electronics chaper.<br /><br />Thanks again,<br /><br />Shane
 

petryshyn

Commander
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Oct 3, 2001
Messages
2,851
Re: Coil Reversal -- Please Help!!

If you are testing the coil primary windings, set the meter to the lowest scale (X10 in your case) then connect the leads together and zero the meter. Then procede with the test. Multiply your reading by "10"<br /><br />The best way to test a coil is to swap it into another working cylinder and see if the problem follows. An ohmmeter can show up certain types of deficiencies, but not all.... :)
 

clanton

Rear Admiral
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Jul 9, 2001
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4,876
Re: Coil Reversal -- Please Help!!

Looking at Clymer B750, show 2 types of ignition system, one is a standard battery powered system, the other is a magneto system, inportant to know which system on your engine. One way of checking correct coil polarity is hold the spark plug wire about 1/4 inch away from the spark plug termial with the engine running. Insert the point of a wooden lead pencil between the plug termial and spark plug wire. If the spark flares on the spark plug side of the pencil, the polarity is correct, if the spark flares on the wire side, the polarity is incorrect. From Auto engines and electrical systems by Motor copyright 1970.
 

SlowlySinking

Master Chief Petty Officer
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Oct 31, 2002
Messages
897
Re: Coil Reversal -- Please Help!!

Hi Turtle, if you follow schematic's advice on the meter use and your last comments you will be in the right direction. Don't feel too bad about your electronics knowledge, many years ago when auto mechanics started being tested to get ASA certified less than 4% passed the electrical part of the tests. Give it a go and let us know what you find. With all the knowledgeable folks on this forum we should be able to get this done even by remote control. :) After all they got Apollo 13 repaired the same way.
 
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