Alan: Because with ANY amount of fuel in the tank, if it is capped and vented normally, the ratio of fuel to air (oxygen) */inside/* the tank is never near that required for ignition. Way too rich, in other words, like killing a running engine by pulling the choke full on despite the spark plugs firing normally. If it is a fuel sytem which has vapor recovery and recirculation into the tank, there is never much air (oxygen) entry except when being filled, and even then fuel vapor is being expelled by the added fuel, discouraging air entry.
Even a tank with an open or missing cap */but some fuel/* will never reach an ignition capable ratio of fuel vapor to oxygen /*inside*/ the tank. It can be lit from the filler tube and will burn, but can be extinguished by putting something over the filler tube - even your hand if you don't mind a little singe. It won't explode immediately as some think. (some personal experience here long ago to back that up) However, in an accident circumstance where the tank is ruptured and fuel is spread, then yes, it can reach an ignition ratio quickly - but that is not what you were asking. That is why an old fuel tank is dangerous to cut open with a torch or abrasive disc - even if considered empty for a long time - a more favorable fuel vapor to air ratio can exist until no more fuel vapor is present inside. (I am a couple years more recent than you, so pretty much a kindred spirit) George On 1/17/2015 7:12 PM, alan.c.taylor--- via KRnet wrote: > Mark, > From the day I was born (Sep 1929) I have never been able to get an > explanation as to why the little sparks generated by the old resistive type > fuel senders do not cause an explosion. > My own explanation is that the air/fuel ratio in the tank is too rich to > burn but I can not find any one who will confirm that or deny it. > Can you assist? > > I wish you and yours a happy snd prosperous new year. > > Alan Taylor. Australia > > I wouldn't let electrical connections in the tank worry me much, as long > as the connections are positive and not going to spark. I just replaced > the fuel pump in my wife's fuel tank, and the +/- 12V connections that > run the pump are right there in the tank, submerged most of the time, > but not when it's low on fuel. They are positively screwed down to a > terminal with a nut though. No spark, no worry... > > Mark Langford > ML at N56ML.com > http://www.n56ml.com > > > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options > > > _______________________________________________ > Search the KRnet Archives at http://tugantek.com/archmailv2-kr/search. > To UNsubscribe from KRnet, send a message to KRnet-leave at list.krnet.org > please see other KRnet info at http://www.krnet.org/info.html > see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change > options --- This email has been checked for viruses by Avast antivirus software. http://www.avast.com
