Is it true that a diesel engine can operate underwater?

Under certain circumstances, diesel engines can operate while submerged in water. Find out what it takes to waterproof an engine -- and why diesel engines are better candidates than their gasoline counterparts -- in this episode of BrainStuff.

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Episode Transcript

Speaker 1 (00:00):
Welcome the brain Stuff front House stuff works dot Com
where smart happens him Marshall Brain with today's question, is
it true that a diesel engine can operate underwater while
a gasoline engine cannot. You sometimes see military vehicles running

(00:24):
in extreme conditions, and these conditions can include deep submersion
during a river fording. Creating a vehicle that can run
submerged is a challenge. In order for any type of
combustion engine to run, it must have a source of
air and it must be able to release exhaust gases.
If the water is not too deep a few feet, say,

(00:46):
the exhaust castes can take care of themselves because they
are under pressure. The air intake is usually the problem.
As soon as you submerge the air intake, the engine
can no longer get air and it will stop running.
You can get around the air intake problem by adding
a snorkel. Military humvees often have a snorkel attached and
it allows them to submerge in up to five feet

(01:10):
of water. In order to handle submersion like this, the
engine and the rest of the vehicle must be waterproofed. However,
so your question changes into is it easier to waterproof
a diesel engine than it is the waterproof a gasoline engine.
To waterproof any off road vehicle, there are lots of
different things to think about. For example, any electrical devices

(01:32):
like the instruments, the engine control computers, motors for fans,
windshield wipers and so on, lights, battery, et cetera. All
have to be sealed. Second, any venting for things like
the crank case, the differential and stuff like that must
also be sealed or vented at the same level as
the snorkel. The fuel tank must be sealed invented appropriately,

(01:56):
and any chamber or crevice that can fill with water
must of a drain. Assuming that all these other things
have been taken care of, and assuming that the engine
is waterproof, then the vehicle can run under water. In general,
it's easier to waterproof a diesel engine than it is
to waterproof a gasoline engine because the spark plugs and

(02:16):
ignition system and a gasoline engine are complicated when you
get them wet. These components run at high voltage, and
sealing them is harder, although it's not impossible. A diesel engine,
on the other hand, has no ignition system See how
diesel engines work at how stuff works for details on that.
If the diesel engine has a mechanical fuel pump for

(02:37):
the injectors and a mechanical transmission, there's also no engine
control electronics to worry about. These features can make a
diesel engine relatively easy to waterproof. That's why most military
vehicles that ford rivers or run submerged have diesel engines.
Do you have any ideas or suggestions for this podcast?

(03:00):
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