trouble shooting emergency shut down soliniod

[gus]

The actual normal shutdown is-turning off the electric Engine Run switch cuts off power to an electric solenoid which opens an air valve that lets air onto an air cylinder piston which pushes the spring loaded fuel shutoff inside the engine. Once the air pressure bleeds down the fuel is once again turned on even though the engine is not running. So, the engine is always "On".

At least that is the way the 671 on my 4104 works.

This is the reason you cannot shutoff an engine right after it starts if you have no air pressure.

This has caused a bunch of guys (Including me) to have a mysterious engine  stoppage a couple of minutes after a perfectly normal start and smooth run. After a short time when the air pressure again bleeds down you once agin get the normal, but short, engine run. Very frustrating.

Accidentally hitting the engine shut off switch in the engine compartment will cause this strange and frustrating situation!!