A paragraph in a book I've been sent to review seems to be in error.

Either that, or I'm not properly intuitice about this situation.

The paragraph poses a mulitple choice question. "What is the best way to shut
down a runaway diesel engine?"

One choice is a throw-away. "Cut off the electrical supply." Bzzzt! "Thanks for
playing, and we do have some lovely parting gifts for you........"

The other two choices:

1. Cut off the fuel supply

2. Cut off the air supply

I immediately thought, "the fuel supply. You shut down a diesel by cutting off
the fuel."

According to the author, the correct answer is supposed to be "Cut off the air
supply." The author recommends "discharging a fire extinguisher into the air
intake."

Well, first off it would need to be the correct type of fire extinguisher. Some
extinguishers are charged with halon (which is no longer legal to mfg in the US
but is imported or recycled from other extinguishers) and a diesel will run
like crazy on halon.

And, I'm aware of emergency shut downs that have been accomplished with CO2
extinguishers, etc. I just thought those were cases where it was impractical to
cut off the fuel supply.

Wouldn't putting a postive stop to the fuel supply from the injector pump be a
more certain solution? "Some" air might get sucked into the air intake along
with the fire suppressant, maybe enough to allow the engine to cough past the
extinguisher discharge and keep running. But, the engine absolutely will not
run without fuel.

Shutting off the fuel very far upstream wouldn't be a good choice, as an engine
can run quite a while on the fuel in lines, filters, etc.

Somebody care to agree, disagree, or show me why my preference for fuel shut
down would be wrong?




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