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. > > > > > >To send a message to this group, send an email to: >Chrysler300@xxxxxxxxxxxxxxx > >For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm >Yahoo! Groups Links > > > > > > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Yahoo! Autos. Everything you need to know about buying or selling a car. FREE Quotes, 360° Tours, Research, Blue Book, Compare Vehicles, Buy Used http://us.click.yahoo.com/kEZsdA/bwnGAA/YiGOAA/8LmulB/TM --------------------------------------------------------------------~-> To send a message to this group, send an email to: Chrysler300@xxxxxxxxxxxxxxx For list server instructions, go to http://www.chrysler300club.com/yahoolist/inst.htm Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Chrysler300/ <*> To unsubscribe from this group, send an email to: Chrysler300-unsubscribe@xxxxxxxxxxxxxxx <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/