After a flying session it's routine for me to disconnect the fuel line, put the lead on the plug and hit it with the starter to burn all residual fuel in the crankcase. I was out flying with my son this evening after 4 flights earlier in the day. Two additional flights then the ESV meter says it's time to stop so we start breaking things down for the night.

I announce I was going to pump the remaining fuel out of the tank then run the residual fuel out of the engine. My teenager says, "No, just run it dry now. I want to finish wiping off the plane." So I comply and disconnect the fuel line. I have a fuel filter between the tank and carb and disconnect the tank tube from the filter. Put the lead on and hit it with the starter. Engine fires up but with fuel still in the tank and the muffler pressure line still attached...

See where I'm going?

Sure enough, we start spraying fuel out unplugged line. But the engine doesn't lean out and die. Seems that all this excess fuel being sprayed out the line still attached to the tank is being sucked in by the line still attached to the carb. This is a gap of about 3/4" open air and the darned engine doesn't think anything is wrong - it just keeps running! My son is getting raw fuel and exhaust all over his hands and arms. So I say, "Now what?" There's still over ½ of a tank left.

My brain finally starts working again so I reached down and plugged the carb line with my finger which stops the flow of fuel across open air and the engine finally dies.

I think my son understands now why we empty the fuel tank before doing this. Also wouldn't hurt to disconnect the muffler pressure line.

Luckily all we had happen was a lot of raw fuel to clean off the plane. I wear eyeglasses so I have "some" protection against raw fuel getting into my eyes but my son does not.

Electrics are starting to look more inviting all the time.