[Chrysler300] Things that go Boom

[Rich Barber <barber@xxxxxxxxx>]

It might help in understanding the crankcase explosion phenomenon by 
remembering that it only takes a very small amount of volatile fuel in a 
crankcase to produce a flammable mixture.  And it has to be just the 
right mix of air and fuel and it must have a source of ignition.  Just 
like in a power cylinder, if the mixture is too rich or too lean, it 
will not ignite.  Perfect mixture and no spark, it will not ignite.  It 
is not too hard to imagine a spark from a piston ring in the crankcase.  
That is how they wear out, so we must assume that ignition sources are 
likely.  Blowby of hot exhaust gases past worn or stuck rings can also 
occur, as can small holes in pistons.

Gasoline can enter the crankcase from the fuel pump or past the piston 
rings in some cases.  Gasoline washing the oil off the rings and 
cylinder walls further increases the likelihood of a spark.  Very small 
amounts of gasoline and water vapor from the air are evaporated by the 
hot oil and vented without explosion.  We have all observed vapors 
coming out of the old oil breathers and crankcase vent pipes and the 
vapors are not all oil vapors!   I'm not sure how much air and fumes a 
PCV system inhales, but it may be designed to keep the crankcase 
fuel-air ratio in the too lean to burn range.

Backfire into oil bath air cleaners can also produce under hood fires.

Bottom line:  Thanks to all who shared their horrible experiences.  
There must be many more out there.  All of our 300's are at some risk 
and the older ones are probably at the greatest risk due to lack of 
PCV's and as mechanical wear and electrical system deterioration 
continue.  Learn from these stories and be careful and observant.  Let 
these stories cause a little bell to go off when you are participating 
in problem-solving.  Keep a couple of small fire extinguishers handy to 
minimize damage.

I don't believe they are making any more letter cars so MoPa'r to you in 
keeping yourself and your cars safe.

Rich Barber
Brentwood, CA
C-300

Leggatt wrote:

>Hi All,
>    Dave, I am so very sorry to hear of your misfortune.
>    It appears that Don Verity has zoomed in on the problem but my first 
>experience with this was about 1988 in a boat that was brand new in 
>1986!. As I was running the oil pressure started to drop off (the gas 
>had diluted the oil). I shut it down and the crankcase was over full 
>(big time). Of course it was the fuel pump. The alcohol in the fuel 
>disintegrated the diaphram.
>    The biggest problem was all the little bits of rubber got into the 
>carb. In a boat the fuel filter is ahead of the fuel pump.
>    Since then, I have replaced two rebuilt so-called "alcohol proof" 
>fuel pumps on my old cars. The diaphrams in both were shrivelled up and 
>disintegrated.
>    Greg.
>
>
>
>
>
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