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Ignition coil hookup

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Author

10-10-2004 01:18:25

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Does it matter if the + or - terminal is hooked up to the distributor? Ford '52 8N sidemount distributor.

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souNdguy

10-10-2004 18:00:21

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Re: Ignition coil hookup in reply to JM, 10-10-2004 01:18:25

Did you hook your battery up backwards when you were doing all this?

No starter motor is an odd one.. it will spin the same direction no matter positive or negative ground.

I think you have a few wireing issues.

Soundguy

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MikeT

10-10-2004 09:54:26

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Why would it matter? in reply to JM, 10-10-2004 01:18:25

If the ignition coil is just a primary winding and a secondary winding, then why would it matter? Is there something going on inside a coil that we don't know about? I've never seen a schematic diagram for an ignition coil. Anyone have one? I have seen coils that are not marked with a "+" or a "-", just two unmarked posts and the center high voltage connection. Could modern day coils have a diode inside? Just curious.

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Bob

10-10-2004 12:50:34

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Re: Why would it matter? in reply to MikeT , 10-10-2004 09:54:26

When the coil primary is hooked up correctly, the leading edge of the secondary pulse is negative each time the coil is "fired", and this is applied to the center electrode of the sparkplug.

The center electrode is "HOTTER" (thermally) than the ground electrode. Due to "thermionic emission" from the hotter electrode, it's esier to establish a spark with the current flow in the correct direction. (That's how old-fashioned vacuum tubes worked.)

If you hook up the coil primary in the opposite direction, the voltage pulse at the secondary will be reversed, and the theory is that the spark at the plug will be 20% to 30% weaker.

There's nothing magic here, and no diodes are involved. The polarity of the spark is readily observed on an ignition oscilloscope.

The coil will produce a spark hooked up either way, but hooked up the correct way, the spark is more effective at lighting off the fuel mixture.

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Rob

10-10-2004 11:52:25

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Re: Why would it matter? in reply to MikeT , 10-10-2004 09:54:26

Current flow direction through the secondary would be reversed if the polarity of the coil is reversed. Current flow and polarity would be reversed on the points and condenser.
I can't figure how that would relate to the primary wire from the coil to the distributor. Too much football right now. Anyway, doesn't should like it would be any good.

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MikeT

10-10-2004 11:57:05

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Football? GO ASTROS! in reply to Rob, 10-10-2004 11:52:25

Nuff said!

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Rob

10-10-2004 02:41:56

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It matters some. in reply to JM, 10-10-2004 01:18:25

They went to the trouble and expense of marking it for a reason. Standard 6v wants positive to the distributor.

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txblu

10-11-2004 12:44:47

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Re: It matters some. in reply to Rob, 10-10-2004 02:41:56

You can get Dell to reiterate his previous comments on this, but it has to do with the direction of current (electron flow) in the plug. If going from ground to the center electrode one thing happens, and reversing something else. Think it is migration of material off the center electrode if that is neg. That's why engines used pos grounds with 6v. (as I recall). Then per Dell (I forgot....was too young and stupid at the time), the transistor radio required not only 12v but also neg ground to get the (germanium)output transistor biased properly. (now I remember that). And All along, I thought that 12 volts was to reduce the amount of copper in auto wiring. Dumb me.

Mark

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10-10-2004 07:02:54

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Re: It matters some. in reply to Rob, 10-10-2004 02:41:56

found that out by hooking it up wrong and nothing worked :) Not knowing the internals, assumed it was a loop of wire, besides the NAPA guy told me negative to distributor as mentioned in some previous posts that I looked up on this forum. I guess they forgot it was a positive ground system. Thanks for the post.

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Rob

10-10-2004 07:36:01

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I probably should have worked. in reply to JM, 10-10-2004 07:02:54

Negative to distributor. Just not as well. Weak spark is all I think. You might have another problem.
The insulators on that distributor stud you wire to can be a problem. The slip on the inside gets squished up and torn and it grounds out.
Anyway, good luck with it.

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10-10-2004 07:57:38

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Re: I probably should have worked. in reply to Rob, 10-10-2004 07:36:01

Strange things happened! I thought it would work either way myself, but something seemed to have shorted under the dash, everything went dead. Checked out the wires to see if there was a ground or short, found nothing, switched the coil to positive to the dist. and it fired right up. I checked the post and strip at the distributor, all ok. Any ideas on this?

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Rob

10-10-2004 09:14:58

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Not sure what it is that went dead. in reply to JM, 10-10-2004 07:57:38

You talking about the starter motor, lights, or something else?
I've never hook up that coil back-wards but I've seen guys post that getting the polarity wrong results in a spark that is not as strong. Far as I know that's all you get.
Sounds like you have another problem, an intermittent problem, and you gotta hate intermittent problems.
The wire between the coil and distributor might have gotten up against the hot manifold and now have a bad spot on the back side that will short every chance it gets.
If your starter hangs up and won't turn you need to rework the cables and posts. That type of problem can come and go. You need large diameter cables. Short cables. Bigger around than the 12v cables in your more modern transportation. Compare and see. Get cables marked for 6v and then no longer than necessary. OEM for the 8N is 10.5" for hot and 10" for ground but you might end up with something nearer to 14" from a local auto parts. Be sure they are labeled as 6v cables and they will be big enough around for their length.
The ignition switch is not as robust as some parts so if you continue to have mystery problems get a jumper wire with clips on the end to you can get on that terminal block and jump around the switch to see if that solves the problem. Don't leave the jumper on there all night.

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10-10-2004 09:29:18

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Re: Not sure what it is that went dead. in reply to Rob, 10-10-2004 09:14:58

The starter didnt work, dont have lights. Thanks for the help. I think the voltage reg is what fried, no charging, repolarized by touching bat to arm at the regulator, saw a spark, but nothing at the ampmeter, shows slight disharge while running, like 2 amps.

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Rob

10-10-2004 09:49:39

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Best thing to do there in reply to JM, 10-10-2004 09:29:18

is to take both the regulator and the genny in to the shop. They will test them both together.
Any alternator/genny/starter shop can do you up right. To troubleshoot electrical problems you really need to start with a full charge on the battery because low volts makes things strange.
Make sure the belt is tight. 1/2" slack with moderate pressure 1/2-way between the crank and genny pulleys. You should not be able to make the genny pulley slip using two hands on the pulley.
Quick check for low genny output is to connect a jumper between the armature and field on the genny. Start the engine and check the ammeter, remove the jumper and compare the ammeter reading. If the charging rate increased when you removed the jumper then the genny is ok so check for a regulator problem. That could be bad wiring. Corroded connections and the like. YOu really need a good ground between the genny and the regulator and there should be a forth wire off the reg to the genny that is a ground. If you don't have that wire then paint or rust on mounting brackets or mating surfaces can cause problems, intermitant problems even.
You might need to rework the wiring cleaning and remaking all the terminations. Repair or replace any damaged, worn or corroded wires. A fresh, $15 wiring harness is maybe the best $15 you will ever spend on that tractor. Close second and third are the $15 copper-core plug wires and the $15 for battery cables. Farm/ranch stores should have all of it. Make sure you get the 'after SN ****' (side-mount) harness.

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