841 died and won't start

Hello again friends thank you for your patient help!

The other day I was putting my 172 gas tractor to work disc turning our huge garden, great fun. I still have a 195deg thermostat in there and the engine got really hot but continued to work great. Not sure if that's part of this equation, but it's in here anyway.

Normally, when I start it cold, it will idle then drop and if I goose the choke it will rise up to idle again, I do that few times and when it gets warm I don't have to do that anymore. Yesterday I was looking forward to wrestling with the plow (another story) to get it back on and while warming up, backed out of the barn and around to drop the back blade I had on. It seemed like it should be warm enough but it died while I was positioning the blade to drop it.
When I went to start it again, it wouldn't start. I assumed it was flooded but forgot the oft-repeated method for getting through flooding. Engine rotates but will not start and playing with throttle and choke, I could get it to catch a little but it would die pretty soon. It also had some rough run and backfiring out of the exhaust. Engine refused to keep running smoothly as it had only moments before.
Figured the battery might need a charge (still have a 6v genny on an otherwise 12v system) so I charged it overnight.
Got out there today and it would rotate faster but no start. I could get a little catch and it would gallop with gray smoke coming out of the exhaust, but no smooth idle.
Plug wires are on securely, and I do not believe there is spark jumping the wires, but I haven't tried a darkness + spray bottle to completely disprove that.
The coil was replaced last year, and the nut on the side that goes to the distributor just turns for some reason. Regardless, that terminal does have good contact.
Oil is good level and smells fine, radiator is full, fuel tank is more than half full. Even if there were water in the fuel, I believe it would have worked out by now, I've dumped the sediment bowl a couple times.
I have a serious fuel leak from the sediment bowl (as if the gasket I just replaced last year doesn't work correctly or maybe I'm not tightening the bottom nut enough) so there is at least some reduction to fuel flow. Pulled the carb bowl screw, it flows reasonably well given the sediment bowl gasket issue.

What should I investigate next?

Thank you, and I hope you've got your feet up from a successful day.

The distributor terminal is a problem. If
it's just the nut stripped it isn't
making good contact. If the whole stud is
turning it's shorting out.

Thank you m-man, it's just the nut turning. I'll see if I can lock it down with another nut above it.

When is the last time it's had a good tune-up. New points, condenser (keep the old one), rotor, distributor cap, plugs cleaned and gaped if not replaced? From your story it sounds like the poor thing needs some T.L.C.

I would agree with you, but I did those things last year. I think I will review them though, the problem seems like it's in there somewhere.

Just got out there this evening, fixed up the fuel leak.

Discovered I have no spark.

When I went to gap the points, a small blue spark occurred (so I detached the battery.) Does that indicate the condenser is good?

I'm left with either a bad condensor or a bad coil, or both. I think I'm supposed to check the (internal resistor) coil for resistance. Is there a method for checking the condensor? Jim, I do have the old condensor but it doesn't look very old.

Finally, how do I shop for these items (if needed) at an O'Reilly?

Thanks a million!

Found a method for checking a condensor for function:
https://mgaguru.com/mgtech/ignition/ig129.htm

Also discovered o'reilly part numbers for the condensor (FD75) and internal resistance 12v coil (23-0240) but at these prices, I'm going to order from YT. good to know they're local though.

Bingo, bad condenser. And I've been spelling it wrong.

Now I know how to test them for function and I have two more (in sealed ziplocs from YT/ASAP) for the inevitable future.

Thanks for your help, friends.

Glad you found the problem. I read on here quite often about bad condensers right out of the box. So yours lasted a year or so. Better than some.