Small Engines (Lawn Mowers, etc.): Lawn mower, hp engine, coil ignition

Question
To whome it may concern;
I have inherited a lawn mower, it may have only one or two hrs. of running on it.  But it has a running problem.  It will start and run for about 30 seconds and then the revs slow down and it will stop.  Like it would if the coil is bad, or it runs out of gas.  It has a Tecumseh 3 hp engine with an ignition module, no points.  I tried to remedy the problem.  I put on a new coil (ignition module), substituted the carb, changed the plug, checked the timing, checked the crankcase vent, tank cover vent, everything is okay.  What have I overlooked.  Please help.
Thanks in advance.
Orest.

Answer
Hi Orest,

I would have suspected a faulty ignition, a dirty carb or a fuel tank vent.  Since you have addressed all that, I don't know what to say.  
When it quits re-check for spark and fuel flow issues.  Try to re-start it while squirting fuel or starting fluid into the carb intake.  

Let me know how you make out.
Michael