8n no spark

Started tractor. Started no problem and was running great. While hooking up the brush hog it started cutting in and out and then died. Removed bolt on bottom of carburator, plenty of fuel. Tested spark plug for spark. Not even a hint of spark. Tested coil for spark. No spark. New coil since the one on it was 9 years old. Still not spark. New points and condenser. Still no spark. Ignition switch is only 2 years old. Ammeter shows about 4 amps discharge when running starter. It fluctuates rapidly between 0 and a little below 0. There isn't any markings on the ammeter between 0 and 10. Probably a wiring problem? The harness is all wrapped up and I am not sure where to start talking it apart. Can I test the pos and neg wires on the coil to make sure power is getting to the coil, and what should I expect?
 
late 52 side mount distributor.
Checked switch. terminal to ground, 6.45 volts with switch on.
negative terminal on coil with switch on. 6.1 volts.
positive terminal on coil switch on points closed. No power.
coil terminal on distributor, points closed, switch on. no power.
new points and condenser, and copper strap and related bolts, nuts and insulator installed prior to testing.
Rotor and distributor cap in near perfect condition.
 
I think you need to measure the coil primary voltage with the points open; otherwise the circuit is going to be dragged down to ground voltage.
 
Do you have battery voltage across the points when they are open? (with the points open, put one probe on one side of the points & the other probe on the opposite side of the points) Verify the gap on the points at .025. Then, dress the points by running a piece of card stock or brown paper bag through them. New points sometimes have an anti-corrosive dielectric coating on them & old points can corrode or pick up grease from a dirty feeler gauge or excessive cam lubricant. (I always spray my feeler gauge blade off w/ contact cleaner.) Make sure you have voltage across the points, as in past the insulator on the side of the distributor. That is a very common failure point on sidemounts, along w/ the attached copper strip. It's hard to find a short there because it is usually an intermittent . So 'wiggle' the insulator & the copper strip a bit when you are doing your checking.

If you just replaced the rotor & lost spark, put the old one back in. Insure that the rotor fits firmly on the shaft & that the little clip is there. Make sure the distributor cap is not cracked, doesn?t have gouges in it from the rotor or brass shavings & doesn't have carbon tracks. Check continuity on the secondary coil wire. Make sure it is firmly seated in both the cap & the coil. Next, remove the secondary coil wire from the center of the distributor cap, turn the key on & crank the engine while holding the end of the wire 1/4" from a rust & paint free spot on the engine. You should see & hear a nice blue/white spark. If not, you have a bad coil or condenser. Just put the old condenser back in to eliminate that as a possibility.


Post back w/ results; I'll be interested in what the problem was.
75 Tips
 
Yes, there is voltage across the points when they are open. Fixing problems as I go went like this.
Testing fuel flow to eliminate no fuel triggered a leak at the bolt in the bottom of the carburator. Did I maybe lose a gasket or did I crack the float bowl at bolt? My older carb doesn't have one there. So bought a new gasket set so I could take the carb apart to replace the float bowl due to a crack. Took carb off which involved totally rounding the shoulders off the 7/16th fitting at the carb on the fuel line using a 7/16th open end wrench. Cheap China metal. Replacing fuel line caused pot metal fuel valve to break. Put original back on which I had saved from years ago. Now sediment bowl leaks from new fuel screen and gasket set. Threw out cork gasket and put rubber gasket back in. Put a new fuel line on.
Put new distributer to points parts in including bolt, nuts, insulator and copper strip. Put in new coil. Put in new points and condenser. New dust cap. Still no spark.
Check power everywhere. Power to neg side of coil. No power to post side. Checked continuity in distributor. No short between points and no short between distributor wire and distributor body.
Unwrapped wires front generator to ignition switch. No visible problems. Wrapped wires back up and the lead to on of the screws to the generator, the white wire, fell off. The other lead had 2 breaks in the insulation. Put new connectors on both. Wrapped the breaks with electricians tape. Discarded the new dust cover because it was keeping the rotor from seating completely.
checked power on each side of points and now I have 6.4volts power.
Put old dust cover, rotor, and distributor cover back on, turned on the fuel, turned it on, pulled the chock and hit the starter. After a few seconds of turning over it started. Ran just fine with no problems for about 15 minutes so I put it back in its garage and shut it down. I just don't know exactly what fixed it. Bad and broken leads to the generator? Or a new coil, or both, or some other combination of problems. Anyone want to buy a tractor? I am moving to Florida next springand won't need this one anymore unless the grass starts growing again.
 
The generator is in the charging circuit, tractor will run fine without it.
I'm late to the party, but would have liked to see the voltage
measurements on each side of the coil with points opened and
closed. New points don't always make contact until cleaned.
They also, sometimes, do not mate or open correctly.
 
(quoted from post at 06:23:28 09/19/17) Not sure what you mean. How should I do that test?

Turn the key on and check the voltage on both sides of the coil with the points open. Then repeat w/ the points closed. As I said earlier, you will see battery voltage, points open and about half that with the points closed. But not zero as you were seeing. .
 

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