I have a honda push mower it ran fine except to spit up black fluid under a load, now it stopped running

Here are the details, its a self propelled bagger. The previous owner ran it without a air filter, and judging from the center of the blade hit something pretty good. I ran it weekly on a half acre lot and when I hit a heavy patch of grass it would bog out blow some blue smoke and cough out black fluid from the overflow port next to the intake of the carburetor. Now it just blew a cloud of smoke and died and won't start.

I have changed and drained the old fuel, replaced the spark plug, checked for spark, compression, and thoroughly cleaned out the carburetor. The oil looks like a darkish gray but no shavings. Also when I turn it over with the sparkplug out I barely see any kind of mist shooting out but yet the intake valve moves. What else could it be?

It coil that produces the current for the spark plug