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Loose spark plug wire

J

JoshF

New User
I've got a Farmall 300 that runs great when I hold one of the plug wires about a half inch away from the plug, but when I put it on the plug, it wont fire on that cylinder. It has the old style plug wires without boots so I can't just slip it on loosely. Any way to fix this problem without changing the plug wires? I'd like to keep them original. Thanks
 
Holding the spark plug wire away from the plug makes it fire hotter. So you either have weak spark of a bad spark plug. I would replace the spark plugs and wires.

An old time trick was to take a corn cob. Make a hole down the center. Stick it on the spark plug and the wire in the other end. It would hold the spark plug wire away from the spark plug. That would make it fire.

Grand Dad talked about doing that during WWII when everything was rationed.
 
Never heard of the corn cob trick, but I remember seeing the plug wire cut in two, and the cut ends wired onto a shirt button. The spark jumped across the holes in the button and made a marginal plug run a little longer in a worn out engine. And then there was the little issue about the sediment bowl leaking nearby.
 

Some of the new generation JD gas engines recommended a special spark plug with an internal spark gap to lessen plug fouling. You could identify those plugs by the tiny vent hole in the metal top terminal that vented gasses formed in the internal spark gap.

A spark plug company called Aldor, takes that a bit further. Their plugs also have the internal spark gap inside the insulator, that has some sort or thermal widget that opens the internal gap when the plug is cold, then slowly closes it as the plug heats up. They claim to fire in conditions that badly foul ordinary plugs.
 
40 yr ago the head mechanic in the truck shop showed me that trick. If a gas engine is misfiring you pull a plug wire in turn to find the bad cylinder (most people use that "trick"). Then, if you hold the wire so the spark has to jump a gap, and that cylinder starts hitting again, you know the plug is bad or borderline. But if you can't get the cylinder firing again, you have a bigger problem, maybe a bad valve or some similar mechanical problem.
 
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