Small Engines (Lawn Mowers, etc.): Briggs Vanguard no spark, starter solenoid, volt battery

Question
I have a 16 hp Vanguard and it lost spark, seemingly after it had the wrong ignition switch in it. The model numbers are 303777-0411-01. It had spark then I switched the ignition switch with one that had different wiring position unknowingly. The breaker off the battery lead into the starter solenoid was tripping with the wrong ignition switch in it, so my buddy held it together while he cranked it to see if we would get spark!! The breaker is still godd and maintains contact now. What should I be checking/replacing? Also what does the solenoid in the carb bowl for? It was rapidly clicking for awhile then nothing. I since have reinstalled the original ignition switch, it is ok the ignition solenoid was bad, it also has been replaced. Thank you

Answer
Replaced ignition switch with different one.  No spark, fuel solenoid clicking rapidly.  Did the engine start?  Did you have spark.

Re-installed orginal switch, replaced solenoid.  Does the starter turn the engine?  You now do not have spark.

The fuel fuel solenoid shuts off the main fuel when you turn the key to the off position.  Supposed to prevent backfiring.  The solenoid should have 12 volts DC when the key is in the run position.  If you have two wires on the solenoid, one is ground and one is 12 vDC.  NOTE...poor grounds will prevent the solenoid from opening.  You can check the solenoid with a 9 volt battery.  Battery positive to the wire and battery negative to the ground or metal solenoid case.  You should hear it click.  Parts diagram shows only one wire.

Ignition module check.  Dis-connect all wires connected to the coils.  There should be one small wire connected to each coil.  With the wire(s) dis-connected, check for spark.  If you have spark, the coils are fine and you either have a safety switch problem or a wire harness problem, issue with the diodes.

578 692306 Wire Assembly
578A 692319 Wire Assembly (With diodes)

If the coils are fine,trace the small wires back to the wire harness.  Follow until wires exit the engine...you should see a terminal or screw connector.  Dis-connect the mower chasis harness from the engine.  Check for spark.  Leave the main wire harness dis-connected.  Re-connect the small wires connected to the coils.  Re-check for spark.  If you loose spark, and the main wire harness is still dis-connected, then you know the wire harness (with diodes) is bad.

If you loose spark when connecting the main mower wire harness then there is a safety switch grounding the ignition system.

Do you have a low oil sensor?
Eric