Ignition Circuit "Old" vs "New"

[marc hildebrant]

Group,

My 1931 Deluxe Tudor is wired the "old" way for the ignition circuit, i.e. the circuit does not flow through the Ammeter. A ford Service notice shows how to change it so that the current is measured with the ammeter.

Is there any reason to leave it "as is" ?

Marc

[Kurt in NJ]

leaving it "as is" means you don't have to touch it.

The reasons for changing it--you can tell if the ign doesn't shut off properly because the ammeter shows a discharge (if the engine stops in a place the points are closed)

The ammeter can also tell you that the points are working because the needle will waver as the points open and close (can give you the clue to check the points when it doesn't start)

[Tom Wesenberg]

I agree that it would be good to change it to the correct way for your time period for the reason Kurt listed. Since that was changed by someone, you may also want to check the coil polarity to be sure it's wired correctly.

[marc hildebrant]

Tom,

Good point. I'll also check the polarity (must be in the Les Andrews book somewhere......)

Marc

[marc hildebrant]

Group,

Checked the polarity and found that it was reversed. I used the procedure in the Les Andrews book to check it.

The engine seems to be "smoother" over 35 MPH now. Is the spark now stronger ?

Marc

[Tom Wesenberg]

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Originally Posted by marc hildebrant

Group,

Checked the polarity and found that it was reversed. I used the procedure in the Les Andrews book to check it.

The engine seems to be "smoother" over 35 MPH now. Is the spark now stronger ?

Marc

The spark isn't stronger, but the plugs fire easier when the center electrode has the correct polarity.
do a google search for "chicagolandmgclub.com" and look for checking coil polarity. They have the best explanation I've seen on coil polarity.

[marc hildebrant]

Tom,

I read the story in the MG owners group and I have to say that "I didn't know that ". The story is that a negative going pulse on the center terminal of a spark plug is "easier" than a positive going pulse. Hence the need to have the correct coil polarity.

That explains why I have a smoother engine when I'm "pushing it" around 45/40 at my elevation (5000 ft).

Well, I learned something new...

Marc

[Tom Wesenberg]

Originally Posted by marc hildebrant

Tom,

I read the story in the MG owners group and I have to say that "I didn't know that ". The story is that a negative going pulse on the center terminal of a spark plug is "easier" than a positive going pulse. Hence the need to have the correct coil polarity.

That explains why I have a smoother engine when I'm "pushing it" around 45/40 at my elevation (5000 ft).

Well, I learned something new...

Marc

Here's the link for others that would like to check out the site

http://www.chicagolandmgclub.com/tec...neral/574.html

[zzlegend]

Thanks Tom. Learned something new here. Mark.

[Tom Wesenberg]

Originally Posted by zzlegend

Thanks Tom. Learned something new here. Mark.

You're welcome.
BTW, for anyone checking coil polarity by using a meter as shown, you can protect the meter movment by placing a high ohm resistor between the two meter leads. Something like 1,000 ohms to 10,000 ohms should work and still let you see the needle move a tiny bit upscale. Without a shunt resistor the meter will get all that high voltage and may damage a delicate meter movement. Just bend the resistor ends around the leads where they plug into the meter, then remove it when done.