Ignition issues on Model A

cogosser · Jan 30, 2018

I have an early 40's Model A that I am having issues with the spark. If I pull the plugs and ground them to the frame and crank the engine I have 2 sparks on the left side plug. It has a WICO distributor that was rebuilt with new points and coil. It is a distributor nor a Magneto. Even when I completely remove the right side wire from the distributor, I can still get a double spark on the left side plug. I am thinking I have a cracked distributor cap, but I do not have the tell tale black trace across the contacts. Anyone have any ideas?

Mike M · Jan 30, 2018

I guess I'm not following you ? That model even with a mag. fire on both TDC of compression and exhaust. So they normally spark 2 x ?

Those WICO Dist. were not know to be very good. The Delco Remy is the preferred unit.

cogosser · Jan 31, 2018

[Doesn't the distributor turn at half the speed of the crankshaft? If it does, each plug should only spark once, TDC of its compression stroke.
Why am I getting the spark on the #1 plug on its exhaust stroke?

Mike M · Jan 31, 2018

That model they turn at crank speed.

The crank turns the larger cam gear so that is 1/2 speed, then the cam gear turns the smaller governor gear taking it back up to crank speed.
Models like the 520 thru 730 gas all run the dist. off the cam.

Lee B · Jan 31, 2018

TDC Exhaust stroke spark is for that side and should be there for these double hit girls. Every TDC. Technically called waste spark system it is also used on pony motors and a good number of modern cars too. It's an honest to God real thing and you've got it even if you didn't know it before this point. Sounds like this might be news to you and maybe it's not cross-firing at all?

cogosser · Jan 31, 2018

Thans for your help. I learned something today. I can stop chasing ghost.

erskine2017 · Jan 31, 2018

The Waterloo and first number series tractors whether they have magnetos or Wico or Delco distributors fire on both compression and exhaust TDC. The ignition system is driven by the governor gear at crankshaft speed. Vertical distributors on two cylinder 20 and 30 series turn at one half crankshaft speed. LP tractors of first numbered series also turn at half speed.

John T · Jan 31, 2018

When you say "two sparks" do you realize it fires at TDC on BOTH the Power and Exhaust strokes??? That's IF it has a Wico C or X Magneto or the Wico distributor you have. That's so if you remove one or the other plug wire, the one firing will still fire on BOTH TDC's.

You mentioned "left side plug" it should do the same on the left and right. If you ONLY have fire on one side but not the other, there could be a wire or plug or cap or rotor type or else another problem.

John T

John T · Jan 31, 2018

As I and others noted it fires on BOTH TDC's Power and Exhaust.......

John T

Ignition issues on Model A

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