No Spark Farmall A

Thu Nov 08, 2007 8:10 pm

I am not getting a spark on a farmall A. The magneto has been tested and it is good. The kill switch was tested and it is good. Could it be the spark plug wires? I put them together but maybe I did it wrong. Do I need to cut back some insulation and expose some wire and then wrap it around the tip. The wires are hyphalon ignition wires with copper conductor. Thanks for the help


Thu Nov 08, 2007 8:26 pm

I know this sounds funny but do you have a rotor? If so is the metal end still on it. I have had the rivits rot out that hold the tip on a rotor on a neighbors Farmall C.

Thu Nov 08, 2007 8:38 pm

Yep the tip is still on it. The rotor is brand new

Thu Nov 08, 2007 9:10 pm

Marine1 wrote:Yep the tip is still on it. The rotor is brand new

Is the rotor pointed to a tower when the mag trips? Have you checked for spark directly from the coil?

Thu Nov 08, 2007 9:28 pm

How do I check for spark directly from the coil?

Thu Nov 08, 2007 9:33 pm

Pull the center wire from the distributor and hold it close to ground while cranking the starter over. If you get a spark, your problem is in the delivery system (distributor).

Fri Nov 09, 2007 8:36 am

I am not sure what you mean bigdog. Could you explain it a little more for a beginner? haha


Fri Nov 09, 2007 8:46 am

Have you disconnected the kill wire form the magneto, to see if it is shorted somewhere. The switch on a magneto grounds the wire to kill the engine.

There were a couple of different mags available. If you have an IH H4 magneto there is a cover over the coil on the very top that has a wire running to the center of the distributor cap. Remove that wire from the distributor cap (leave connected to the top cap) and hold it close to the metal case of the magneto (no more than 3/8 inch gap) and crank the engine to see if you have a spark. If not, you have an internal mag problem, points, condenser, coil, etc. If you do have a spark there, the problem is in rotor, cap, wires, etc. If you have a Wico, etc. magneto rather than an IH, the wire form the coil to cap is internal.

As a safety note, there is not a safety gap inside an IH magneto, so when you are trying to fire it, make sure the spark has someplace to go, such as having the wire close, using a spark plug held against the case, etc. Most auto parts stores sell a spark tester which looks very much like a spark plug with a large alligator clip on the side. You can even adjust the gap size to check the spark strength.

Fri Nov 09, 2007 9:05 am

So the wire from the kill switch goes straight to the magneto? I tried to disconnect it but I will try again. I have a spark tester. The one that looks like a spark plug. When I am getting spark how does the tester show it? I will try to use the wire straight from the coil and test for spark. Thanks for your help!


Fri Nov 09, 2007 9:06 am

Aaron - what I am trying to say is that if you are getting a good spark out of the mag - which can be verified by using the lead from the mag coil to the center of the distributor - that means that the components which produce the spark (the mag coil, points, condensor etc.) are functioning. So if you are still not getting spark to the plugs the problem lies in the delivery part of the system which is the cap, rotor and plug wires. The delivery of the spark to the plugs would also include timing issues.

If this doesn't explain it well enough send me a pm and I'll try to go into more detail.

Fri Nov 09, 2007 9:08 am

I understand now big dog. Thank you!