Understanding the solenoid on the carburetor bowl of some new Briggs Engines ?

[preventec47]

I have a year old low end 42in TroyBuilt rider with a 500cc Briggs engine and it suddenly died today and I am trying to trouble shoot it. I believe most likely is is one of the safety
feature implementations that is shutting the mower down and I followed some wires and was shocked to see them terminate at the carburetor on the engine.

Can someone explain what is likely going on here? I can only guess there is a possibility that when the ignition is on that a solenoid opens and when the ignition
is off the solenoid closes. But if that is true, why? where is the safety or what is the benefit etc. ? OR maybe there is another switch somewhere that is operating
the solenoid. I dont see how it could be safety related because I cannot imagine a carb solenoid reacting fast enough to shut down an unsafe operation....

Ultimately is is something that I can disable or hardwire to improve reliability ? Is this solenoid implementation becoming standard on other brands of mowers as well ?

 

[dougand3]

It's a fuel shutoff solenoid. Main purpose is to stop after fire (some call backfire) when you turn key off. When you remove spark (key off), you still have fuel dumped into the intake, which travels un-burned to the muffler and BAM! It should also prevent crankcase filling with gas from a leaky needle/seat. WHOA! I've got 2 quarts more oil than needed! Kinda thin, too.

 

[bertsmobile1]

Doug got it 1/2 right.
IT will not stop the engine filling up with fuel because the fuel will flow up the air vent on the float bowl .
Because of new EPA regulations that vent has to be on the inside .

 

[dougand3]

Thanks for clearing that up, Bert.

 

[Jpow]

I had to cut the plunger within the solenoid off and install a fuel shut off valve to get mine to start and it has less than 100 hours. Tried doing all the logical stuff (plugs, filters, gas, carb) etc. It would only start when I hit it with starter fluid which I know is bad for the engine. Starts and runs like a new one now.

 

[TDHofstetter]

Doug and Bert both have it partway wrong. The afterfire solenoid only hinders (but does not stop) fuel flow to the main jet. It doesn't prevent fuel flow through any other path from the tank to the crankcase... and there are several.