Any suggestions?

Thanks in advance

Jerry

Could this be something to do with the ignition module, causing a weak spark, that disappears after the start handle is released?

I can see no points or condenser, just a coil and a second smaller coil off to the side.

There is a coil underneath the flywheel, with a smaller coil / condensator sitting right next to it. I don't see any points.

I have not yet replaced the rubber bowl gasket, don't believe that would kill the engine after 2 seconds.

No secrets.

At one time I was able to keep it running with quick start.

The alternate carb I tried was from a Sears engine also 5 hp, also Tecumseh. Symptons didn't change

The throttle plate is closed just sitting there but when the engine is cranked I see the plate on top move open.

"No varnish or corrosion present as everything has been cleaned with carb cleaner." Well, corrosion doesn't come out w/ standard carb cleaner. The thing to know here is that Tecumseh carbs are not clean up friendly. Water damage is irreversible.

"There is a coil underneath the flywheel, with a smaller coil / condensator sitting right next to it. I don't see any points." The only coil that I'm familiar with that is under the flywheel would be the ignition coil. The breakers are under the cover that goes over the crank. Electronic ignition on these are external of the flywheel and no condenser is used. A smaller coil should be the charge coil for the battery. Maybe a light file on the points would help, tho the point and condenser are cheap enough. It should ground when the breakers close. You can simply unhook the condenser for a test. It would probably be old enough not to have the "T" style flywheel key? Which by the way are available in 2 versions that don't interchange.

"I have not yet replaced the rubber bowl gasket, don't believe that would kill the engine after 2 seconds." It's like this: A Tecumseh engine will run with an improper bowl seal, yes. Not always well as it changes the environmental rules set by the guy who designed it. A pitted bowl or a deteriorated seal will allow it to lose its e.i. It won't prime properly however, so if you had gotten it started by using carb spray- it would continue to run.

"At one time I was able to keep it running with quick start." I do suggest carb spray as a tamer version of quick start. How long did you have it running for? And how long ago was this? Has the machine sat? These are important questions. Look at it this way. If it starts and runs as long as you are directly providing the "fuel"- then you know you have spark and compression.

"The alternate carb I tried was from a Sears engine also 5 hp, also Tecumseh. Symptons didn't change." And this engine runs well currently?

"The throttle plate is closed just sitting there but when the engine is cranked I see the plate on top move open."
This engine will want to start when the throttle plate is open only. I assume this thing has a throttle cable. Maybe do a test and prop the throttle shaft 1/4 or so open and try starting.

My responses are getting as long as Mownies- yikes!