Cant't get a spark from my JD B

Since we already know you have voltage to the coils input, now place that meter or a test lamp at the coils output terminal which leads to the distributor. It should normally be ZERO since its connected to ground via the points EXCEPT for when the points open on cam ready to fire the coil. (not usually there, cuz pistons dont stop at TDC on compression often) NOW, if it never goes to ZERO volts there (as you rotate the engine) although the points appear closed, there must be a loose or missing wiring connection from distributor to points ORRRRR theres bad oxidation on the point surfaces. (or they are not closing period) If they never fully close (the coil doesnt get a current path to ground) and the voltage at the coils low side doesnt get to zero (points have it to dead ground) youre not gonna get a spark.

NEXT, if a test lamp at the coils low distributor side is ALWAYS zero, it agian will never fire. The points have to close and the coil conduct current and THEN they have to open (points on high cam) to fire the coil. If its always zero there, there could be a shorted wire to the points or the condensor is dead shorted.

Clean the points with a light to non abrasive so as to NOT remove the silver coating, gap them to 0.020, check to insure no wires to points or condensor are grounded and check to see the condensor or its wirign are NOT shorted, and if she still wont fire, post back and we will guide you through testign the coil and other things. Good luck and God Bless Ol John T Nordhoff in Indiana

~Are you sure you have the flywheel in the correct place for the L/H [flywheel side] cylinder to spark? If the L/H piston isn't at TDC the points can't close when you rotate the distributor because the points cam won't be in the correct location to allow the points to close. Watch the points as you rotate the distributor to see if they are actually closing. If not you don't have the flywheel in the correct location [L/H piston at TDC].

~Use a test light or volt meter & see if you have battery voltage to the coil ignition switch side terminal , if so, then see if you have voltage to the point side terminal of the coil. You should have power on the distributor side with the points open that goes away with the points closed. If you always have voltage on the points side you have a points wiring, points oxidation problem, or open in the wiring. If very little voltage is on the distributor side even with the points open you have an improper ground at the points wire stud, shorted condenser, grounded pigtail between the coil & dist, or open in the coil.

How can I clean the points to remove the oil or film? Also, if the points are gapped at 015 and not 022 can this cause no spark?

~To clean the points, use contact cleaner, brake clean, or alcohol & a clean piece of white paper. Don't use any sand paper, or other abrasive as that can effect the points coating on new points. If you do use a sandpaper type product don't use anything with metal oxide in it. Make sure to COMPLETELY remove any sandpaper residue & then run a clean paper between the points. The use of sandpaper will allow the points to oxidize much quicker the next time.

~With the ignition on, rotate the flywheel or distributor until the points are open, then pull the coil wire from the distributor cap & hold it within 1/8" of the engine, then use a screwdriver to wiggle [short] between the points to see if you have a spark, if so do the same by turning the distributor. If it sparks with the screwdriver but not when turning the distributor you either have dirty points or they aren't closing properly.