Farmall H with a distributor.Starts easily, but only firing on 3 cylinders. When I remove the #3 lead to the distributor and hold it about 3/8 of an inch from the cap, the engine smooths out and speeds up. When I insert the lead into the cap, as it is supposed to be, the engine slows down and starts missing. Traced the cause to a loose fitting rotor, but can't understand why it wouldn't hit on all 4 with the lead in place. Help, and thank you.
- Thread starter Dr. Bert
- Start date
Allan in NE
Well-known Member
Fouled plug.
Allan
Allan
Janicholson
Well-known Member
I will add to Allan's correct answer.
The typical issue is oil fouling today. When leaded fuel was used it could be lead deposits, or oil fouling. The oil "cokes" carbonizes, leaving a conductive path on the insulator. When the gap is made large by pulling off the lead a ways, The coil then increases its voltage to jump that gap as well as the plug gap (and fouling) thus the plug fires the fuel/air mix. Replace the plug, and all is better. If it fouls that plug again, it might be telling you it needs a valve job to fix excess guide wear (if it smokes more when idling) or a ring job as well if it shows blue grey smoke under load. Jim
The typical issue is oil fouling today. When leaded fuel was used it could be lead deposits, or oil fouling. The oil "cokes" carbonizes, leaving a conductive path on the insulator. When the gap is made large by pulling off the lead a ways, The coil then increases its voltage to jump that gap as well as the plug gap (and fouling) thus the plug fires the fuel/air mix. Replace the plug, and all is better. If it fouls that plug again, it might be telling you it needs a valve job to fix excess guide wear (if it smokes more when idling) or a ring job as well if it shows blue grey smoke under load. Jim
Just to add one more tid bit to the correct answers......When the coil fires the voltage IS NOT instantaneously at say 10,000 volts, it begins to ramp up until its high enough so current can arc jump the open NON conductive plug gap HOWEVER if theres a conductive path due to oil or carbon (fouling) the coil starts to conduct current and thus expends its energy and never rises up to the high voltage to arc the gap. When you introduce that added extra gap current cant flow through the oil/carbon so the voltage does rise until POW it fires the plug.
John T
John T
Robert Major
Well-known Member
Hi
Will just add something an old guy told me 25 years or so ago, in the old days of tractors fouling plugs when they wore out. Some guys would cut the wire and then take a shirt button. Bare the ends of the wires thread both wires through the opposite holes. This then permanently created the gap like you pulling the wire. The motor would then get the hot spark and not fowl plugs, and run until it was totally worn out.
If you see a tractor or old engine in a sale with shirt buttons in the wires run. Chances are it"s totally worn out and gonna need a full rebuild.
Regards Robert
Will just add something an old guy told me 25 years or so ago, in the old days of tractors fouling plugs when they wore out. Some guys would cut the wire and then take a shirt button. Bare the ends of the wires thread both wires through the opposite holes. This then permanently created the gap like you pulling the wire. The motor would then get the hot spark and not fowl plugs, and run until it was totally worn out.
If you see a tractor or old engine in a sale with shirt buttons in the wires run. Chances are it"s totally worn out and gonna need a full rebuild.
Regards Robert
todd hamilton
Member
Remember too these old engines were built to plow all day and run hot. The iron content in the blocks make them sweat and draw moisture when not running. Work your tractor hard every chance you get, it will run better. Put some marvel mystery oil in the gas it will help the valves and rings seat like they are supposed to.
"George Meissner, in the early 1900"s, fretted over this problem, as have most modem enginemen.
He noticed, as many modem enginemen have, that by pulling off the spark plug wire and creating a small gap between the wire and the plug, that an engine with a contaminated plug would sometimes fire.
Mr. Meissner, however, took the idea one step further, built a spark-gap attachment, and patented the idea."
Invented a hundred years ago...
He noticed, as many modem enginemen have, that by pulling off the spark plug wire and creating a small gap between the wire and the plug, that an engine with a contaminated plug would sometimes fire.
Mr. Meissner, however, took the idea one step further, built a spark-gap attachment, and patented the idea."
Invented a hundred years ago...
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