200 Coil Update

Time for me to eat crow! I took the coil and had it tested at an auto electric shop late yesterday. Problem was that it was right near quitting time and they did not sell coils. They checked the resistance of the primary and secondary but something just did not seem correct about their procedure. They told me they got an open circuit on the primary and 5+ ohms on the secondary. I think they just wanted to get rid of me so I went to an electronics store and bought my own test meter. The correct readings for my coil were 1.3 ohms on the primary and 56,000 on the secondary. The 1.3 is in range for the primary and I would bet the 56,000 is in range for the secondary for a 6 volt coil. At this point I would have to say it was not the coil and I did not get a new one! I will keep you updated as I do additional testing. Thanks again John T. and all of you who insisted that the problem would not be the coil.

Thanks for the update, all we can do is take you at your word when you give us data (about coil etc), then we reply based on what you tell us.

CHECK THE POINTS be sure they arent badly burned or pitted (might be able to file them if so) and close down properly. If they are gray oxide coated run a dollar bill through them which can clean them. A COMMON PROBLEM IS BAD POINTS

Ive posted this information for you and others, but people must not be able to open it or whatever, so I'm copying and pasting some (applicable to your situation) portions of my Troubleshooting Procedure below. If the coil IS NOT the problem run my Troubleshooting Procedure.


1) THE VERY FIRST THING YOU GOTTA HAVE is voltage to be present on the coils high supply (NOT to distributor) terminal when you turn the Ignition switch ON. If not she cant ever fire, but in the event the ignition switch or circuit/wire down to the coil or any Ballast Resistor is bad or open, you can HOT WIRE it by jumping a hot ungrounded battery voltage source to the coils high input supply (NOT to distributor) side n see if she runs then???? If she fires hot wired, you could have a bad ignition switch ((That can happen, when Ignition is on, the switches IGN terminal must turn hot)),,,,,,,or an open Ballast (if it has one) or a bad/open wire from switch to coil.

If the switch is good, if you turn the ignition switch on and place a test lamp on the coils high (NOT to distributor) terminal SHE MUST LIGHT UP. If not again, look for an open Ballast Resistor (if it has one, it should read around 1.25 to 2 ohms across its terminals) or bad/open wires from the switches IGN output down to the Ballast (if it has one) and distributor.


2a) When the Ignition switch is turned on, voltage should appear on the coils high input side. That would be 6 volts on a straight 6 volt system or 12 volts on a 12 volt non external ballasted system, or around 6 volts on a 12 volt system that used a 6 volt coil plus an external Ballast Resistor and the coil is good and the points are closed and they and ALL wiring is good.

2b) DELETED SINCE YOU SAY COIL IS OKAY


3) Next, place your voltmeter or test lamp over on the coils other low to distributor terminal side, turn her on and crank the engine over.

4) A test lamp there should flash ON (when points are open) and OFF (when points are closed) as the engine is cranked slowly.

5a) If the lamp never comes on there, the coils primary is bad/open,,,,,,,,,,or the points are never opening,,,,,,,,,or theres a shorted/bad condensor (remove its lead to points and see if lamp comes on, if so, bad shorted condensor or its wiring),,,,,,,,or the points wire is shorted,,,,,,,,or the distributors side pass thru stud is grounded (use ohm meter to test that),,,,,,,,,or the points may have a shorted spring.

5b) If the lamp never goes off as engines cranked, the points are not closing or are bad,,,,,,,,or the wire or circuit is missing from the distributor to the points,,,,,or the distributors not well grounded to the tractor.

She cant fire the coil unless its low side is getting a conductive ground return path via closed points and then the circuit is open when the points open.

Be sure the condensor or its wiring is NOT shorted out and see if the lite comes on (when points open) with the condensor disconnected. If removing the condensor makes her spark, replace the condensor.

SUMMARY

Be sure the points are closing fully and open on high cam and ARE NOT BURNED OR PITTED OR CARBONED UP BADLY,,,,,,,theres voltage present on distributors high side at all times when ignitions on (or its a bad switch or open ballast or bad wiring to col),,,,,,,voltage on coils low side flashes on and off as distributor is cranked,,,,,,,,,condensors not bad/shorted,,,,,,,,no shorts in wires to points and no shorts in pass thru side out distributor stud,,,,,,,,coil has continuituy.

John T
John Ts Ignition troubleshooting

Take your coil to a marina or small engine shop that has been in business for a long time. ask if they have a Merc-O-Tronic coil tester; This will perform a maximum secondary voltage output test (the spark you want) as well as primary voltage and leakage tests.
I use mine frequently to check old & newer coils for performance.
TEST, DON'T GUESS!!!

Good point, an actual HV Coil tester is the way to really know and test under actual High Voltage conditions. A low voltage low energy continuity test can tell if a coil is definitely BAD (like an open winding) HOWEVER its common for an actual failue to be due to high voltage breakdown and a continuity or ohm meter test doesn't indicate that test.

IE an ohm meter test cant tell you if a coil is really good even if it passes primary and secondary resistance checks.

John T

I have an old set of points [polished surfaces] & condenser out of a 6 & 12 volt system set up with jumper wires terminated with alligator clips for testing coils. By flicking the points open & closed, the coil high voltage can be estimated by the color of the spark---or lack thereof. Use the coil wire held 1/4 inch from the coil case to check output.
Not fool proof, but tells if your coil is putting out or shot. Doesn't tell if troubles from heating the coil after a long run is what is causing trouble.