I did say that the pump was cooled by fuel.
I wasn't disputing that - I should have worded it differently - something like "You said that the fuel cools the pump, and that is true. But all of the parts in the pump and the motor...actually live in (are wet with and totally surrounded by) the fuel."
I know that on a return style system you can have pump failure when cold fuel hits a hot pump,...
Though ours doesn't have a return loop all the way from the fuel rail, it is return in that the pressure regulator located in the fuel pump assembly dumps the excess immediately back into the tank - a "loop" of less than a foot. Not sure how our pump can get hot enough that more fuel flowing thru it could cause a failure. Trying to think of how that would come about, but I don't see it. The pump would only be generating heat when it's pumping, and whenever it's pumping, fuel is flowing thru it, cooling it (yes - as you said).
What about when the pump is running with the tank empty - you do have the column of fuel still in it, but it's not flowing, so the pump would heat up - right? No - because the PCM will disable the pump from running more than a second or two at a time when you first turn the key on and, until it detects that the engine is actually running, will keep the pump from running any further - hence no heat buildup. I just don't see any scenario of cold fuel hitting a hot pump and causing any type of failure on our cars.
...Mix vapors with oxygen and then all you need is a spark, the spark doesn't have to be the brushes contacting the commutator, I should have said assembly not motor,...
I'll buy that.
More than likely it would come from the current flowing threw the fuel level sending unit contacts.
Not sure there's enough current to cause any spark there, but for sake of argument, OK. Probably more chance of static from your clothes setting it off.
It is possible, and thats why you use nitrogen and not oxygen to do evap tests. We learned a lot of lessons from a little car named pinto.
Are you saying that they used to use oxygen for evap tests? Whoah! That is crazy.