1939 Distributor Problem
- Thread starter Porsche
- Start date
BillM
Well-known member
I don't believe you can damage a coil by connecting it with the wrong polarity. Like other kinds of transformers it has a soft iron core that has the magnetic property of being easily magnetized and de-magnetized, so there will be no lasting effect of reversed polarity.
Hi there, I agree with the above statement. I have worked on car electrics for more than 50 years and NEVER EVER had an issue with an ignition coil where the polarity of the battery in a car has been reversed. Of course the coil primary connections should preferably be change around as well. Over the years we changed the batteries on many English cars to negative ground from positive ground and never had a problem with the coils. I am thinking that Bubba posted information on this topic, which was the first time I have ever heard of it. Maybe he could give us some proof of this situation. Best regards, Kevin.
BillM
Well-known member
Actually if you research a little farther you will find that it is really the spark plug that is polarity sensitive. The coil puts out the same voltage; but with opposite polarity. See http://mgaguru.com/mgtech/ignition/ig104.htm
JSeery
Member Emeritus
Yep, I agree. Was mainly referring to coil damage. Guess it would be better to refer to the reduced performance as an ignition system issue. Interesting article thanks for posting it.
theHIGHLANDER
Senior Member
It's supposed to be positive ground. Nobody answered that part of this which I find unusual.
JSeery
Member Emeritus
Don't understand this comment, but it is true that the car should be positive ground. Believe Porsche knew that from the get-go and corrected it as soon as he noticed the error.
"The executor whom I purchased the car from had a new 6 volt battery installed as a negative ground. The car was driven a few times short distances before I purchased it saw the error and changed to a positive ground.
Do not know if this could have caused some damage."
BUBBAS IGNITION
Well-known member
Polarity??
A coil aqquires some residual magnetism over a period of time. Once a given polarity is put into a coil either positive or negative then that coil will retain that polarity.
When reversed the coil loose some of its output. Some GM bullitins say as much as 80% of the maximum output. Polarity over the years has been reversed by incorrect wiring on factory cars. The effect was a more frequent tune up needed.
Lets say the coil has a reserve max out put level of 25,000 volts from the factory, reversing the polarity would lower the max output to 5-10,000 volts.
If you kept your car tuned you might not ever notice the difference.
However underload ( when you might need the extra voltage) and acceleration it might miss fire.
As i find some spare time i can hook up a scope and fire a test plug to show the actual differences firing in a backwards polarity.....
A coil aqquires some residual magnetism over a period of time. Once a given polarity is put into a coil either positive or negative then that coil will retain that polarity.
When reversed the coil loose some of its output. Some GM bullitins say as much as 80% of the maximum output. Polarity over the years has been reversed by incorrect wiring on factory cars. The effect was a more frequent tune up needed.
Lets say the coil has a reserve max out put level of 25,000 volts from the factory, reversing the polarity would lower the max output to 5-10,000 volts.
If you kept your car tuned you might not ever notice the difference.
However underload ( when you might need the extra voltage) and acceleration it might miss fire.
As i find some spare time i can hook up a scope and fire a test plug to show the actual differences firing in a backwards polarity.....
BUBBAS IGNITION
Well-known member
Another observation , over the years we have tested a lot of early Ford helmet coils on our Allen coil tester.
If i forget and wire it negative ground they usually put out less spark than if i wire it positive ground. Nowdays i check both directions just to make sure the coil is good...
BTW did we ever get this car running ???????????
If i forget and wire it negative ground they usually put out less spark than if i wire it positive ground. Nowdays i check both directions just to make sure the coil is good...
BTW did we ever get this car running ???????????
flatheadmurre
Well-known member
Theres a big difference between a ignition coil and a normal transformer.
The normal transformer has ac going through with a reversing magnetic field.
The ignition coil has a chopped dc and the magnetic field just rise and fall.
The normal transformer has ac going through with a reversing magnetic field.
The ignition coil has a chopped dc and the magnetic field just rise and fall.
Bruce Lancaster
Member Emeritus
Engine, from what I can see on tag, seems to be a wartime Canadian 239, distributor is '42-end of war Canadian iron crab.
On removing the distributor...though you have a tighter engine compartment, I believe you can remove it the same way I would on my '48 without much trouble. It will only be hard the first time...once you see how it all goes you'll be able to do it in the dark.
Pop loose the clips holding cap and push cap forward loose.
Remove distributor bolts...one you can see, other is 180 around. Open end wrench.
Note how rotor is pointing...distributor will only go back on the right way, and seeing where it is in its rotation will help you get there.
Wire (primary) is already off. stick fingers into gap between cap and distributor, push rotor forward and off. cap can stay there, dangling on its wires.
Wiggle distributor forward a very short distance and it's loose, weasel it out sideways and you have it, now easy to work on. R&R does NOT affect timing.
On re-installation, get rotor into about same position you noted earlier, push distributor towards its seat, and go back and forth with rotor until tab slips into its slot.
On removing the distributor...though you have a tighter engine compartment, I believe you can remove it the same way I would on my '48 without much trouble. It will only be hard the first time...once you see how it all goes you'll be able to do it in the dark.
Pop loose the clips holding cap and push cap forward loose.
Remove distributor bolts...one you can see, other is 180 around. Open end wrench.
Note how rotor is pointing...distributor will only go back on the right way, and seeing where it is in its rotation will help you get there.
Wire (primary) is already off. stick fingers into gap between cap and distributor, push rotor forward and off. cap can stay there, dangling on its wires.
Wiggle distributor forward a very short distance and it's loose, weasel it out sideways and you have it, now easy to work on. R&R does NOT affect timing.
On re-installation, get rotor into about same position you noted earlier, push distributor towards its seat, and go back and forth with rotor until tab slips into its slot.
Bruce Lancaster
Member Emeritus
The first time you attack one of these things, it looks impossible to service. Once you have been through the minor tricks to removal, you can get it off in about a minute by braille and have it comfortably inside the house to rebuild. You may find this easier, in fact, than draping yourself over the fender to service a more modern distributor...
Ford released a "field expedient" timing system in its 1946 service book...I suspect this came out of WWII. I've checked this and a similar method foe '32-41 distributord against a KRW Ford timing fixture, and all is good. It is summarized online here:
http://www.vanpeltsales.com/FH_web/flathead_engines_distr-timing.htm
You will find a lot of other good information on that site.
Ford released a "field expedient" timing system in its 1946 service book...I suspect this came out of WWII. I've checked this and a similar method foe '32-41 distributord against a KRW Ford timing fixture, and all is good. It is summarized online here:
http://www.vanpeltsales.com/FH_web/flathead_engines_distr-timing.htm
You will find a lot of other good information on that site.
Well I finally got the car going again yesterday.
Thanks to everyone for their input.
A special thanks to my friend Ted who was a big help on this issue.
It does not appear that it was a single problem but a combination of little issues.
To recap - the car had been running last summer and then after sitting for three weeks it would not start.
Through the process of elimination I changed the coil and condenser. Still no start.
Removed the distributor. Points were corroded so they were cleaned up and re gaped. Plugs were fouled. Cleaned and re-gaped them.
Still no start. Cleaned the connections to starter and coil and after some coaxing got the car running again.
Drove the car for about 30 minutes. Shut if off and it started right up.
Better than my 2008 car.
Now I am going to proceed to clean every electrical connection on the car. Hopefully this will keep things working.
Of course it is now almost winter so it will not getting any use til the spring, but hey it is running!!!!
Thanks to everyone for their input.
A special thanks to my friend Ted who was a big help on this issue.
It does not appear that it was a single problem but a combination of little issues.
To recap - the car had been running last summer and then after sitting for three weeks it would not start.
Through the process of elimination I changed the coil and condenser. Still no start.
Removed the distributor. Points were corroded so they were cleaned up and re gaped. Plugs were fouled. Cleaned and re-gaped them.
Still no start. Cleaned the connections to starter and coil and after some coaxing got the car running again.
Drove the car for about 30 minutes. Shut if off and it started right up.
Better than my 2008 car.
Now I am going to proceed to clean every electrical connection on the car. Hopefully this will keep things working.
Of course it is now almost winter so it will not getting any use til the spring, but hey it is running!!!!