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Spark problem

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pgapinski

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could someone explain to me wh

could someone explain to me why a automotive style plug starts my 71model 40 Merc. but not a perma-gap WILL GIVE MORE INFO IF NEEDED
 
"Start with your model/serial.

"Start with your model/serial.

What do you mean "automotive" style plug? as compared to a perma gap?? (surface gap??)

The 71, 40 horse models originally called for a Delco V-40FFM plug - what are you running???

Don't get sucked into using a "cross reference" - cross ref'd plugs DO NOT work with Merc ignitions...."
 
"Here, what I wrote into anoth

"Here, what I wrote into another forum with no response..Model 40, Serial #3032636 4hp that ran on perma-gap plugs that ran for 30+ yrs. I believe it's the original AC- v40ffk. I can only get it fired up if I have it wide open while pulling the recoil. I gave the motor to a guy I work with and he fixed the brittle wires going to the coil and regapped my points to .022 (he said that they were a little pitted). After fixing the diaphram and the wires, it won't run. It pops once and that's about it. I've tried 3 new NGK's and I still get the same response. However, while my coworker had it, he put a fouled NGK plug from his boat motor in (the one's that look-like an automotive plug) gapped at .035 and with one pull it starts up."
 
"The ignition on your particul

"The ignition on your particular model is a kinda hybrid from the time it was produced, what is referred to as a Thunderbolt 2 system.

There is a capacitor built into the stator which stores up the energy generated, when the points make contact it is released to the coil, upconverted to near 40,000 volts and fires the plug. At least that is the way it is supposed to work.

From what you describe it sounds like the voltage coming down the wire is somewhat less than that - which would explain why the spark can jump a somewhat smaller gap (which would exist on the fouled plug) or even a gapped plug compared to the distance it must jump on a surface gap.

The fault could lie in either the capacitor or the coil, or even the wiring in between.

If the coil is the culprit that is an easy fix as it is still available. If your capacitor is starting to go then you are out of luck - the stator is discontinued and sold for over 300 bucks when it was available.

Your alternative is to continue using the fouled plug until whatever component is starting to fail gives it up completely..."
 
"Thanks Graham Lamb for giving

"Thanks Graham Lamb for giving me an idea where to start. I might start with a new coil,or double check that the fouled plug will not burn up the rings or something because of heat ratings some plugs have..After all the coil is orignal and it's had a good life if it is finally getting weak.
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