Weak spark - electronic ignition - backfire

Jimbro · Jan 8, 2021

I have an 8n I changed to a 12 volt. I often have starting difficulties... I added an electronic ignition... it never started better... for 3 or 4 uses over a month. I was caught in a drizzle ... it backfired and died. Wouldn't restart. It did start a couple of days later but with difficulty and then died again after a half hour or so. I had already added new plugs and cleaned the carb. I am assuming it is the coil burned up... I checked it this morning before sunrise to get a good look at the spark... very weak spark.
Could the backfire have been caused by the damp conditions? Could the backfire damage the electronic ignition. I've looked at the distributor... looks in order? I am not sure of the proper resistence going to the coil? Any answers appreciated.

old · Jan 8, 2021

Front or side mount distributor?? Cap could have gotten wet and also have a crack which could cause a backfire an it to die. Also if you have the wrong type plug wires on that system it will kill the Electronic ignition system

TractorTucker · Jan 8, 2021

If you changed it to 12 volt but kept the 6 volt coil and didn't install a resistor it could be you fried the coil.

Steve@Advance · Jan 8, 2021

When you changed to 12v, did you replace the coil or add a resistor?

It needs either a true 12v coil that doesn't need a resistor, or add a 1.5 ohm resistor to reduce the voltage to the 6v coil.

Running a 6v coil with electronic will overload the electronic circuitry and fry it, and or the coil.

Backfiring is a symptom, not a cause. Exhaust backfire is almost always a result of weak or intermittent spark filling the exhaust with unburned gas.

You can also check the voltage at the coil. Ground the - primary terminal, ignition on, with a 12v coil no resistor, should get near battery voltage. A 6v with a resistor should have 6-8 volts. Wiggle the ignition switch while testing to be sure it makes good connection. Work quickly, the coil will overheat while the ignition is on. Speaking of heat, a healthy, properly powered coil will run about the same temperature as the surrounding components. if it is uncomfortable to hold, it's too hot.

David G · Jan 8, 2021

I agree with old, sounds like wet cap or wires.

Weak spark - electronic ignition - backfire

Jimbro

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old

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TractorTucker

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Steve@Advance

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David G

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