Table saw wired for 220 but using a standard 3 prong plug

Very true. I guess I was assuming (oops) the seller was being smart about it. I gotta stop doing that.

Reply to
Joe
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Now *I'm* rotfl! reminds of a line in the mythbusters show. "once you let the magical blue smoke out, things no work anymore"

jc

Reply to
Joe

I worked as a Metrologist in a fuel pump test facility for one of the big US car companies for 10 years, so I might have the long sought answer to your question.

The somewhat simplified answer, without going into all kinds of details is:

When you run out of fuel there are still a lot of vapors in the tank. Fuel vapors are heavier than air and so they pool in the tank. That leaves an oxygen lean environment.

The chances of getting a combustable mixture into the fuel pump and then a hot enough spark from the brush at the that instance are extremely unlikely.

I suppose it is possible for that big bang to happen but probably only likely on a full moon, during the vernal equinox, South of the equator.

Then you'd have to put the magic smoke back in...

You are correct that the fuel provides lubrication and cooling for the pump motor. We had some guys take old fuel pumps and try to use them to pump water and they don't last very long nor do they pump well. Water conducts electricity a lot better than gasoline...

Lloyd Baker

Reply to
scouter3

I'll take your word for it as it is indeed beyond me and you seem to have the credentials to back up the explanation. BUT while it seems like it would be a once in a blue moon condition that may lend itself to an explosion these type pumps have been used for decades concerning GM cars. It seems likely with the millions of cars produced during that time there surely would have been several once in a blue moons occourances. I have never heard of that happening.

Reply to
Leon

Hi Leon,

There are some other safety features designed in that take the probability of a major thermal event occuring to near zero. I just didn't want to go into them all.

The commutators and brushes are positioned and selected to provide a minimal spark magnitude to further reduce the likelyhood of combustion. The area inside the pump where any combustion would begin is very small. It would be a little bang so to speak. The pump body is a heavy steel and there is a check valve to prevent any flame from the little bang from escaping the pump body and getting into the tank.

Further because the fuel vapors are heavier than air it would take a long long time for them to escape from the tank and allow enough oxygen to enter and form a combustable mix. The car would likely have to sit out of gas with the gas cap off for months or years. The pump would have to pull the air mix into the brush chamber. That would again take a long time to draw the air in because the fuel pump isn't designed to move air. So it would take a long long long time to get the right conditions for combustion.

I add that I was not a fuel pump engineer so there are more things that I am forgetting about or probably don't even know about. I designed calibration systems to ensure that the measurements made by the fuel pump testers were accurate and precise, so I was somewhat on the perifery of the fuel pump's inner workings. I spent some time on a team trying to solve why ethanol was destroying the early electric fuel pumps and got to know the inside of a fuel pump pretty well from that experience.

And ethanol comes from plants and wood does too, so now we're back on topic...

Reply to
scouter3

Thank you LLoyd, those comments above, especially the one about the check valve are probably what I was looking for in an explanation.

Reply to
Leon

Glad I could help. I rarely have enough expertise to contribute much on this group but I really enjoy reading and learning from all of the others.

I hope someday to be able to escape the high tech rat race and have time to woodwork again for fun.

Reply to
scouter3

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