Farmall 300 still weak spark ???

Sooooo o is that spark good n visible n blue orrrrr r a weak faint thin wimpy yellow?????

If its good out of the coil but not any plug wires (bare end to 1/8 from steel) the problem HAS TO BE the cap or rotor or the plug wires IFFFFF FFFFF when the points just break open the rotor tip is lining dead up with one of the caps internal tower pick ups, is it????? If the rotor tip is in between towers and the spark has to jump such a huge gap, its gonna be weaker.

I say you FIRST gotta get a good spark out of the coil wire,,,,, ,,,,, ,,,, and thennnnn nnnn see why its not good at the plug wires, such as caused by the wires being bad,,,,, ,,or the caps cracked or carbon traced or moist or dirty,,,,, ,,,,or things are out of time such that when the points break open the rotor tip isnt in line with a tower. Its not too hard with the plugs out to get the engine turned where the points are just opening and then observe where the rotor tip would be in relation to a cap tower AND TS GOTTA BE LINED UP. If it is and the cap n rotor are all good n clean n dry but still a weak spark out of the plug wire ends CHECK THE PLUG WIRES and use wire core NOT carbon core suppressor wires.

One other thing,,,,, if the condensor is weak but NOT dead shorted, the sparks not as strong as with a good and correct sized condensor, are you sure you have a good and the correct sized condensor????? Also, try a new set of plugs, maybe they are fouled ESPECIALLY if the plug wire end has a good sprak but not the plugs

Let is know n hang in there

John T

Next possibilities (you claim a different coil made no diference) are a weak condensor or a high resistance shorting path somewhere between the coils low (to distributor) side terminal and the igniton points terminal,,,,, ,,or burned points,,,,, ,,or a resistive ground path in the distributor to its ground.

Hot wire the coil again to insure a good voltage supply to its input,,,,, ,,try a different condensor,,,,, ,,,,check the wires from coil to distributor n to the points for any weak links or shorts including the insulated pass through wiring stud on the side,,,,, ,,,use a jumper wire to establish a good ground for the points,,,,, ,,,,,give her 2 aspirins n call me at the Office as Im about runnin out of smarts here lol

John T

With your ignition switch on, measure the voltage
to the coil. Should be near the same as your battery. I guess you now have the starter off the tractor. If it doesn't start or even fire within a couple of engine revolutions there's no need to keep cranking the engine. Have you had the distributor out since this problem started? Hal