M Farmall with really weak spark

I am a real rookie on antique tractors, but i inherited a 1950 model M Farmall. With help I overhauled it and converted it to 12 volt negative ground. It has a very weak spark and is way low on power when under load. It was reccomended to me that I should buy the Electronic Ignition kit offered on this site. My question is which one will I need, has anyone used it, and do you think it will help?

Thanks in advance

Tony Morris

If the low level of power is due to the weak spark, electronic ignition will probably help. Putting new components in your points ignition will cure the spark problem also. There is nothing wrong or obsolete about points ignition, and what you have in your tractor is no different than what powered automobiles up to the early 70's.

You converted it to 12 volts, but did you change the ignition coil to a 12 volt, or add an in-line resistor to drop the voltage to the coil?
Also, when you switch from positive ground to negative ground, you need to reverse the wiring on the coil at the same time or you will have a weak spark.

Electronic ignitions are vastly over-rated.

With a name like Rusty Farmall I am guessing you have experience. I know we put a resistor and I think we put on a new coil. I cannot say we changed the wires on the coil. Is it too late just to switch them and try. Will I screw anything else up?

Tony Morris

rusty knows his way around a tractor!!!! you can try and switch the coil wires around and see if that helps, coil may still be good, also check the 12v coil that ou bought, see if it is internally ballasted, if so, it will not need the external resistor.

Tony - You won't screw anything up reversing the primary wires on the coil. (Incidentally the coil will still spark OK even if it's wired backward).

I'd check the coil carefully to make sure it actually requires an external resistor (photo). If it does not, delete the resistor! Also make sure the points are correctly gapped (.020) and the condenser is good.

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A good coil, points, condenser and wiring will provide more than adequate spark for an M - electronic ignition is really NOT necessary!

What is your definition of a weak spark? low power? Was the tractor adequate before the change to 12 volt? Electronic ignition is not the cure. Maybe it needs a PROPER tuneup,maybe plug wires?.... Wayne

Wayne,
Your point is well taken. I deducted it had a really weak spark from two things. One it is hard starting and must be practically starved for fuel before it does start. Any choke or throttle will flood the motor before it starts. The second thing is it is really low on power. It cannot pull itself in 5th gear at all. I can't describe what it does only to say that when you really load the motor it pops and pukes acts like it is flooding. I have changed plugs/wires/points and condenser. I was told to go up a heat range on the plugs, but haven't (champion D16 are in it). I think it is possible I didn't gap the points correctly. When I do that do I set them so they don't ever close completely?

Okay, you're basing "weak spark" on assumptions. Spark is not where the power comes from. The BANG the spark creates is where the power comes from. If there's too much, or not enough, fuel in the fuel-air mixture, the bang will be weak, and the engine will not produce power.

If you want to verify the spark quality, remove a plug, put it back in the boot, and lay it against the engine block. Have someone hit the starter button while you watch the plug. Make sure the tractor is in neutral because it could start on 3 cylinders. You could disconnect the remaining 3 plug wires from their plugs to prevent that, just remember where they came from. I'll bet the spark is bright blue, which is perfect.

Unfortunately, your local advice, the one that's telling you to "go up a heat range" is just guessing. Whether that's because he's just taking your word on what's wrong, or he's trying to get rid of you, or he's trying to sell you more parts, or he's just clueless, is irrelevant. The heat range of the plugs is neither the cause nor the cure for this problem.

I believe you have a fuel delivery problem. The tractor won't start unless you "starve it for fuel" and will "flood" when you give it any choke at all. A carburetor service (I despise the word "rebuild" because all you're replacing is a few gaskets) including disassembly, cleanout, reset the float, etc. is in order.