Where is my spark going????????????

gmccool

Well-known Member
While bring a wagon from one farm to another farm my 870 gas 8spd it just quit like I shut the key off. It would turn over but wouldn't start. I buddy of mine stopped by and said my aftermarket electronic ignition went bad. So I bought a new electronic ignition and installed it. It still won't start so I got out my test light and here is what I found.

Key off. No power at the coil.
Key on. Power to one terminal of the coil.
Key in the start position. Power to one terminal And pulsating power to the other terminal of the coil. But no power coming out of the distributer or plug wires.
What am I missing here.

FYI plugs, wires and cap are a little over a year old. Thanks Gerald
 
Sounds like the coil may be bad. Might need to find what the specs are for it and do some testing to be sure instead of guessing. Unless you had another coil to try it
 
GM, I looked back in your posts just to get an idea of how in depth that the mechanical projects you get into may be. I did not find anything to suggest you really get very deep into mechanics. So with that I am going to apologize ahead of time if this offends you in anyway. Now this may just be the wording you chose but it sounds like you are checking the high voltage spark that comes from the coil out to the distributor cap by using a test light. This will not work particularly if you have a test light with an incandescent bulb. That type of bulb with essentially a fine wire filament simply shorts out the spark to ground. Aside from having a test spark plug grasping the coil wire by the insulation about an inch back from the end and holding it an 1/8 to 3/16 inch away from bare metal to see the spark jump the gap is the way to do it. Many coils have cadmium plated brackets that are a good bare spot to test spark jump to. Again sorry if I am stating a known fact. I am not real sure what would happen to a modern LED test light if it is subjected to high voltage spark. Hope this helps! Attaching a wire to the power terminal on the coil and running it back to the operators platform so you could connect your test light there would be a way to verify the ignition is continually being powered. Power dropping off would be caused by faulty wiring or a bad ignition switch.
 
Look for rusty or corroded points, condenser and wire contacts. A condenser failure can cause this
And often a voltage drop in the wiring and grounding. Usually it is in the primary wiring from ignition to and including the points and condenser. Coils rarely fail a reason to suspect primary ignition.

But first:

If I suspect an ignition power supply issue I simply remove the positive wire on coil + and run a jumper from the battery for test purposes. If it starts you know which way to go and cost nothing to perform.
There is a whole lotta crap that the ignition feeds under dash. Many points for wrought and corrosion to cause low voltage issues. This is absolutely the 1st no start test I do on old Gassers.

Always ck. Fuel supply.
 
I missed the electronic ignition.
It must be a pertronix unit. I would still run a wire to the coil from battery and disconnect
The feed from the key. This will get you going in the right direction.
Low voltage can still run a test light but not be adequate to Run your ignition. This is why it is important
To hook it to battery direct. If it runs you have wiring issues from your key, Green wires, rusted wires.
Resistor, fuse blocks. Anything is suspicious on old tractors.

Coils can corrode inside where the coil wire plugs in. Cap and rotor contacts.
Good battery to block ground is essential.
If it is pulsating at the a Negative side of coil I would suspect what I have listed.
Also a free test is if the positive terminal on the coil will light up a fog lamp, or spot lamp it has plenty ground and voltage to run an ignition. Again corroded wiring might fire a test light but not carry enough amperage to run an ignition. It certainly wont run a lamp at 7 amps.

Good luck ...
 

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