The capacitor can be easily tested using a simpson meter.
Put the meter on the highest ohms setting (typically RX10K) and connect the capacitor to the test leads. The needle should blip upwards for an instant, and then fall back to infinite ohms.
If it does not blip upwards, or if it reads less than infinite resistance on that scale, it is probably bad.
The mag coil probably has three leads - one that goes to gnd, one that goes to the points, and one that goes to the plug.
You should read an ohm or so between the ground lead and the points lead. You should read several thousand ohms or so between the plug lead and ground.
If either reads dead open, then that's a fail.
If the HT lead reads low resistance to ground, that's a fail.
There are ways to measure the HT insulation of the potted coil but that requires a specialized instrument called a "megger." If for some reason the motor starts and runs fine when cold, but quits when hot and cannot be re-started, due to lack of spark, that is a classic sign of failed insulation on the HT side of the coil.
Normally, I clean up the points with a small piece of very fine wet/dry paper folded over to do both sides at one time, followed by clean, dry plain paper to remove debris. I also apply one drop of instrument oil to the cam follower plunger. Gerry :-)} London, Canada
After reading all the other posts I have to agree with the solid state ignition. But last summer I paid only 10 bucks for a generic one. Works great. But before you do that, did you check to make sure the points actually open and close? On the older Briggs engines with points the little phenolic rod which rides on the cam ground into the crankshaft can get stuck so that it won't move or will not move quite enough to actually close the points. Make sure it is free. ERS
You're talking about the Mega-fire ignition. I've used them in the past and didn't like the results. They're ok if you're good and strong but they take a lot faster spin of the engine to give spark than either a points ignition (takes the least) or a true electronic coil. If you scroll down that same page you'll see what I mean about coil prices.
I've worked on small engines professionally for going on 25 years now and I get to order the coils at dealer pricing. But I still have to get retail for them to make any money and even after market coils list for at least $35 for the cheapest.
Actually I wasn't specifically meaning Mega Fire, I'd never heard of them until today. I bought a generic module that requires just a gentle pull to fire up my mower. It is only about 5/32" thick so a lot smaller than the Mega-Fire. Original lasted about 15 years.
Along with all the other good advice you've received... Make sure the coil mounting screws and surfaces are clean and shiney. The mounting of the armature is actually the ground and by cleaning up the mounting screws/posts, you may get your spark back. HTH Ken.
The same flywheel magnets are used for both. The coil just senses when the flywheel magnet passes. No modification needed. Just bolt in place of the old coil.
One side note here is that while on a points ignition if the flywheel key is sheared then you loose spark. On the other hand with the solid state ignition it doesn't matter and it will spark even if it's 180 deg out. This can be confusing sometimes when trouble shooting and you've got a engine that runs but just doesn't run well.
Second side note is that if you don't tighten the flywheel nut up enough the flywheel key will shear the first time it's started.
The Mega Fire isn't much bigger than that if I remember correctly. What you used is just a copy of a Mega Fire. They where the first that I know of.
As for the gentle pull you have qualify that. A gentle pull for you could be unachievable by some old lady. I can make a points ignition fire every time by just flipping the flywheel by hand. A proper electronic coil can be made to fire that way as well but it's not as reliable. A add on electronic like you're talking about won't even start to. In fact experimenting with the ones I did install showed that the rope had to be pulled at least twice as fast when compared to a proper electronic coil.
If you want to add on electronics to a coil I recommend using Briggs method which was a module that slipped on the coil with a hall effect sensor. These essentially turn a points coil into the same thing as a modern electronic coil. In fact they where how Briggs first came out with electronic ignitions. However I doubt they came be purchased anymore. At least I haven't tried in years now.