Hi Folks---We have a Farmall B or C that the student rebuilt his distributer with new parts and now--we get spark for 6 to 8 revolutions at the points--then we lose spark? Have checked a lot of things with multie meter. Coild has power going in and out 6.2 volts and 6.2 to dist --and 6.2 when points are open. But we lose spark. The coild warms up a little which tells me there must be a ground problem somewhere in the dist. Looking for ideas. Yes--We tried different dcondesnros too--but same result. Is the Coil maybe shutting dowon on me after a few revolutions?--has origiranl coil??

First order of business -- if the seat is in the midle and the steering shaft runs down the left side it's a C or SuperC. If the seat is on the right and the shaft runs dewon the right, it's a B or BN.

Now on to the question. If the distributor was rebuilt, I'd rule out excessive wear on the shaft and bushings, whcih might have been my first guess otherwise. If you can feel a difference in temp in the coil in just those few turns, I'd tend to think his coil is shot. I'm not sure what a bad ground in the points would contribute, but it might be worth checking out the routing of the primary wire from the points to the coil, just to make sure you don't have a short along the way. That's more of a problem with mags where that wire runs through an internal channel than it is with battery ignitions, but worth checking nonetheless.

Put a test lamp on the distributors lil side input terminal or else the coil terminal that wires to the distributor, turn the ignition on and crank the engine over (could remove high voltage coil lead so it dont start) and the lamp should flash ON when points are open but then dead OFF when they are closed.
If the light fails to go off the points arent closing fully,,,,,,,, or the distributor dont have a good ground. If it fails to light up the points arent opening,,,,,,,or theres a short like maybe the distributors lil side stud is shorted to case (broken plastic insulator etc),,,,,,,,or the coils primary winding is bad/open..

On a 6 volt coil the primary between the 2 lil terminals ought to read around 1.25 to 2 ohms.

Id make sure the side input stud isnt shorted,,,,,,the dist has a good ground,,,,,,,the points open n close as they should,,,,,,,,the condensor isnt shorted out. If you remove the condensor n she always fires (even tho a weak spark) try yet another condensor.

Its possible when a partly bad coil or condensor warms up they can fail but it takes more then a few minutes before that normally happens. If theres no shorts n the ground is good and its NOT a condensor problem it could be a bad coil.

To be sure its NOT a cap or rotor problem remove the coil wire where it connects to dist cap (leave coil end intact) and place that wire 1/8 away from tractor iron n crnak ehr over n see if she keeps firing????? If so there but NOT with the wire replaced and youre looking for sparks at plug wires n they stop, suspect a cap or rotor problem.....

If you need my entire Troubleshooting Procedure for non sparking post back

John T